Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/30—Pretreatment of the paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/30—Luminescent or fluorescent substances, e.g. for optical bleaching
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/12—Coatings without pigments applied as a solution using water as the only solvent, e.g. in the presence of acid or alkaline compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
  • D21H19/828—Paper comprising more than one coating superposed two superposed coatings, the first applied being non-pigmented and the second applied being pigmented
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Definitions

• the invention relates to a novel method for producing coated paper, which is characterized by a particularly high degree of whiteness.
• the invention further relates to papers which are produced by this method and the printing of papers which are produced by this method.
• Paper coating slips essentially consist of a mostly white pigment, a polymeric binder and additives which influence, for example, the rheological properties of the coating color and the properties of the surface of the coated paper in the desired sense.
• additives are often referred to as "cobinders”.
• the binder fixes the pigments on the paper and ensures the cohesion in the coating obtained.
• Coating with paper coating slips gives base papers a smooth, uniform white surface.
• the paper coating slips also improve the printability of the paper.
• papers are often also coated twice or three times, that is to say that a coating slip is applied a second or a third time to a paper which has already been coated or "pre-coated".
• white toners fluorescent or phosphorescent dyes
• optical brighteners are added to the coating slip, especially those which are to form the top layer.
• dye-like flu- orescent compounds which absorb the short-wave, ultraviolet light which is not visible to the human eye and emit it again as longer-wave blue light, as a result of which the human eye is given a higher whiteness, so that the degree of whiteness is increased.
• optical brighteners used in the paper industry are mostly 1, 3, 5-triazinyl derivatives of
• optical brighteners in the coating slip only leads to optimal success if they are present in the finished coating of the paper in an optimal structure, conformation and distribution, because e.g. in the case of stilbenes, only the trans form is optically active and only fluoresces to a maximum if it is monomolecularly distributed and held in one plane (KP Kreutzer, basic processes of paper production 2: interface processes when using chemical aids, H.-G. Völkel and R. Grenz (ed.), PTS Kunststoff, 2000, PTS manuscript: PTS-GPE - SE 2031-2).
• Suitable cobinder can be water-soluble polymers, e.g. B. Use polyvinyl alcohol, carboxymethyl cellulose, anionic or nonionic degraded starches, casein, soy protein, water-soluble styrene-acrylate copolymers and copolymers containing acrylic esters (see e.g. K. P. Kreutzer, loc. Cit.).
• activators are polymeric compounds, the problem of which is that they increase the viscosity of the coating slips. As a result, there are tight limits to increasing their application rate in order to achieve a higher whiteness.
• Particularly effective regarding Activation of optical brighteners are paper coating slips with polymers and copolymers containing N-vinylformamide. contain polymerized, as described in the German application with the file number 100 55 592.6.
• the object of this invention was to develop a method with which the whiteness of coated paper can be increased.
• a process has now been found for the production of paper coated with a coating slip containing at least one optical brightener, in which raw paper or pre-coated paper is treated with at least one substance prior to application of the coating slip containing optical brighteners, which has the effect of optical brighteners strengthened.
• polymers and copolymers contain at least one N-vinylcarboxamide, e.g. of the formula (I), in copolymerized form, bring about a particularly strong improvement in the properties of the coated paper if, according to the invention, they are applied to the raw paper or pre-coated paper before the paper is coated with a coating slip which contains at least one optical brightener. In particular, brightness and / or whiteness are increased.
• R 1 and R 2 independently of one another denote hydrogen or Ci to C 2 o ⁇ alkyl, where the alkyl radical can be straight-chain or branched.
• R 1 and R 2 are preferably, independently of one another, hydrogen or Ci to C o-alkyl, particularly preferably hydrogen or Ci to C-alkyl, very particularly preferably hydrogen or methyl and in particular hydrogen.
• R 1 and R 2 can also together form a straight-chain or branched chain containing 2 to 8 carbon atoms, preferably a chain containing 3 to 6 and particularly preferably a chain containing 3 to 5 carbon atoms. If necessary, one or more coal Substance atoms can be replaced by heteroatoms, such as oxygen, nitrogen or sulfur.
• radicals R 1 and R 2 are methyl, ethyl, iso-propyl, n-propyl, n-butyl, iso-butyl, seAr-butyl, tert-butyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-decyl, n-undecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl.
• radicals R 1 and R 2 which together form a chain are 1,2-ethylene, 1, 2-propylene, 1, 3-propylene,
• N-vinylcarboxamides of the formula (I) are N-vinylformamide, N-vinylacetamide, N-vinylpropionic acid amide, N-vinylbutyric acid amide, N-vinylisobutyric acid amide, N-vinyl-2-ethylhexanoic acid amide, N-vinyldecanoic acid amide, N-vinyldodecane acid amide, N-vinyl stearic acid amide, N-methyl-N-vinyl formamide, N-methyl-N-vinyl acetamide, N-methyl-N-vinyl propionic acid amide,
• N-vinyl formamide N-vinyl acetamide, N-methyl-N-vinyl formamide, N-methyl-N-vinyl acetamide, N-vinyl pyrrolidone or N-vinyl caprolactam are preferred, and N-vinyl formamide is particularly preferred.
• the pre-coated or uncoated paper is coated with other water-soluble compounds known as activators for optical brighteners before coating with the coating slip, the contains least one optical brightener, treated, according to the invention an increase in the brightness and whiteness of the coated paper is obtained.
• activators are polyvinyl alcohol, carboxymethyl cellulose, anionic or nonionic degraded starches, casein, soy protein, water-soluble styrene-acrylate copolymers and copolymers containing acrylic esters.
• such polyvinyl alcohols can be used as activators which have degrees of polymerization in the range from approximately 500 to 2500, corresponding to molar masses from approximately 20,000 to 100,000 g / mol.
• the degrees of hydrolysis of the polyvinyl alcohols which can be used according to the invention are generally at least 70 mol%, preferred polyvinyl alcohols have a degree of hydrolysis of either 98-99 or 87-89 mol% and, as mostly partially hydrolyzed polyvinyl acetates, have a residual acetyl group content of approx. 1 - 2 or 11 - 13 mol%.
• the polyvinyl alcohols which can be used according to the invention predominantly have 1,3-diol units, the content of 1,2-diol units is generally below 2%, preferably below 1%.
• Polyvinyl alcohol is understood here to mean a polymer which comprises at least 10% by weight, preferably at least 20% by weight and particularly preferably at least 50% by weight and in particular at least 90% by weight, based on the polymer, of vinyl acetate in contains a polymerized and optionally cleaved form.
• Unitika Poval® Unitika
• Elvanol® Du Pont
• Gelvatol® Gelvatol®
• Lemol® Lemol®
• carboxymethyl cellulose such products can be used according to the invention as activators which have a molar mass of 50,000 to 500,000 g / mol.
• the carboxymethyl cellulose can be used as the sodium salt or as the free acid or as a mixture thereof, preferably as the sodium salt.
• the degree of substitution of carboxymethyl groups per anhydroglucose unit can be between 0.5 and 1.5.
• anionic or nonionic starches degraded as activators for example, hydroxyethyl, hydroxypropyl, methyl, ethyl or carboxymethyl starches can be used according to the invention, which have a molar mass between 50,000 and 2,000,000 g / mol.
• acrylic ester-containing copolymers are understood to be copolymers which contain at least 10% by weight, preferably at least 20% by weight and particularly preferably at least 50% by weight and in particular at least 70% by weight, based on the copolymer, of at least one acrylic acid ester contain polymerized form, for example methyl acrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate.
• Acrylic acid, methacrylic acid, acrylonitrile, vinyl acetate, vinyl propionate, N-vinylformamide, allylacetic acid, vinyl acetic acid, maleic acid, fumaric acid, N-vinyl pyrrolidone or hydroxybutyl vinyl ether can be contained in polymerized form as further monomers.
• These acrylic ester-containing copolymers can be used, for example, in the form of their aqueous solutions or dispersions with a copolymer content of 10 to 75% by weight, preferably 20 to 60% by weight.
• Acrosol® brands from BASF AG are preferably used here, for example Aerosol® A30D, A40D, B37D, C50L or E20D, preferably Aerosol® C50L.
• polyvinyl alcohols and / or (co) polymers which contain N-vinylcarboxamides in copolymerized form are preferably used, particularly preferably (co) polymers which contain monomers of the formula (I) in copolymerized form.
• N-alkyl-N-vinylcarboxamides and their polymers and copolymers are also known or is carried out by known methods, see, for example, Kirk - Othmer, Encyclopedia of Chemical Technology, 4th Edition, Volume 24, J. Wiley & Sons, NY, 1995, N-vinylamide polymers, page 1070; Uchino, N., Machida, S., Japan. Kokai JP 51100188 (CA.86: 73393) or DE-A 42 41 117.
• the production of polymers and copolymers of N-vinylpyrrolidone is known, for example, from the Handbook of Water-Soluble Gums and Resins, Robert L. Davidson ed., McGraw-Hill, New York, 1980.
• Polyvinyl alcohol has been manufactured on an industrial scale since 1939 and has been used in paper manufacture for many decades (Handbook of Water-Soluble Gums and Resins, Robert L. Davidson ed., McGraw-Hill, New York, 1980).
• the (co) polymers which can be used according to the invention can be obtained, for example, by (co) polymerizing
• Examples of monomers of group a) are the above-mentioned N-vinylcarboxamides of the formula (I).
• the monomers mentioned can be used either alone or as a mixture with one another to prepare the copolymers. From this group of monomers, preference is given to using N-vinyl acetamide, N-methyl-N-vinylformamide, N-methyl-N-vinyl acetamide, N-vinylpyrrolidone or N-vinylcaprolactam and particularly preferably N-vinylformamide.
• the copolymers contain the monomers of group a) in amounts of 5 to 100, preferably 30 to 100 mol% in copolymerized form. Monoethylenically unsaturated carboxylic acids having 3 to 8 carbon atoms and the water-soluble salts of these monomers are suitable as monomers of group b).
• This group of monomers includes, for example, acrylic acid, methacrylic acid, direthylacrylic acid, ethacrylic acid, maleic acid, citraconic acid, methylene malonic acid, allylacetic acid, vinyl acetic acid, crotonic acid, fumaric acid, mesaconic acid and itaconic acid. From this group of monomers, preference is given to using acrylic acid, methacrylic acid, maleic acid or else mixtures of the carboxylic acids mentioned, in particular mixtures of acrylic acid and maleic acid or
• the monomers of group b) can be used either in the form of the free carboxylic acids or in partially or completely neutralized form in the copolymerization.
• the neutralization of the mono-ethylenically unsaturated carboxylic acids for example alkali metal, alkaline earth metal bases, ammonia or amines, e.g. Sodium hydroxide solution, potassium hydroxide solution, soda, potash, sodium hydrogen carbonate, magnesium oxide, calcium hydroxide, calcium oxide, ammonia, triethylamine, ethanolamine, diethanolamine, triethanolamine, morpholine, diethylene triamine or tetraethylene pentamine.
• Copolymers contain at least one monomer from group b) in an amount of 95 to 0, preferably 70 to 0 mol% in copolymerized form.
• the copolymers of monomers a) and b) can optionally be modified by using at least one other monoethylenically unsaturated compound which can be copolymerized with monomers a) and b) in the copolymerization.
• Suitable monomers of group c) are, for example, the esters, amides and nitriles of the carboxylic acids given under a), for example methyl acrylate, ethyl acrylate, methyl methacrylate, methyl methacrylate, hydroxyethyl acrylate, 2- or 3-hydroxypropyl acrylate, 2- or 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, 2- or 3-hydroxypropyl methacrylate, hydroxyisobutyl acrylate, hydroxyisobutyl methacrylate, maleic acid monomethyl ester, maleic acid dimethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, 2-ethyl
• monomers of group c) are acrylic idoglycolic acid, vinyl sulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrene sulfonic acid, acrylic acid (3-sulfopropyl) ester, methacrylic acid (3-sulfopropyl) ester and acrylamidomethylpropanesulfonic acid and monomers containing phosphonic acid groups, such as vinyl phosphate, allyl phosphate and acrylamidomethane propanephosphonic acid.
• phosphonic acid groups such as vinyl phosphate, allyl phosphate and acrylamidomethane propanephosphonic acid.
• suitable compounds from this group are N-vinyl-2-methylimidazoline, diallylammonium chloride, vinyl acetate and vinyl propionate.
• N-vinyl-2-methylimidazoline diallylammonium chloride
• vinyl acetate and vinyl propionate Of course it is also possible
• mixtures of the said monomers of group c e.g. Mixtures of acrylic esters and vinyl acetate, mixtures of various acrylic esters, mixtures of acrylic esters and acrylamide or mixtures of acrylamide and hydroxyethyl acrylate.
• monomers of group c preference is given to using acrylamide, acrylonitrile, vinyl acetate, N-vinylimidazole or mixtures of these monomers, e.g. Mixtures of acrylamide and vinyl acetate or mixtures of acrylamide and acrylonitrile.
• the monomers of group c) are used to modify the copolymers, they are present in the copolymers in amounts of up to 30 mol% in copolymerized form, preferably in amounts of 1 to 20 mol%.
• copolymers of the monomers a) and b) and, if appropriate, c) can further be modified by carrying out the copolymerization in the presence of at least one monomer from group d), which are compounds which are at least two ethylenically unsaturated have non-conjugated double bonds in the molecule.
• the use of the monomers of group d) in the copolymerization causes an increase in the K values (see below) of the copolymers.
• Suitable compounds of group d) are, for example, methylenebisacrylamide, esters of acrylic acid and methacrylic acid with polyhydric alcohols, such as glycol diacrylate, glycerol triacrylate, glycol dimethacrylate, glycerol trimethacrylate and at least twice polyethylene glycols esterified with acrylic acid or methacrylic acid or polyols, such as pentaerythritol and glucose.
• Suitable crosslinkers are also divinylbenzene, divinyldioxane, pentaerythritol triallyl ether and pentaallylsucrose.
• water-soluble monomers such as glycol diacrylate or glycol diacrylates of polyethylene glycols having a molecular weight of up to 3,000. If the monomers of group d) are used to modify the copolymers, the amounts used are up to 2 mol%. If they are used, they are preferably present in the copolymers in copolymerized form in an amount of from 0.01 to 1 mol%.
• Examples include homopolymers of N-vinylformamide, copolymers of N-vinylformamide, acrylic acid and acrylamide, copolymers of N-vinylformamide, acrylic acid and acrylonitrile, copolymers of N-vinylformamide, acrylic acid and vinyl acetate, copolymers of N-vinylformamide, acrylic acid and N-vinylpyrrolidone , Copolymers of N-vinylformamide, acrylic acid, acrylonitrile and vinyl acetate, copolymers of N-vinylformamide, acrylic acid, acrylamide and arynitrile.
• the acrylic acid can be completely or partially replaced by methacrylic acid.
• Acrylic acid or methacrylic acid can be partially or completely neutralized with sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide or ammonia.
• the copolymers are prepared by known free radical processes, e.g. solution, precipitation, suspension or emulsion polymerization using compounds which form free radicals under the polymerization conditions.
• the polymerization temperatures are usually in the range from 30 to 200, preferably 40 to 110, particularly preferably 40 to 100 ° C., if appropriate under reduced or elevated pressure.
• Suitable initiators are, for example, azo and peroxy compounds and the usual redox initiator systems, such as combinations of hydrogen peroxide and reducing compounds, e.g. Sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate and hydrazine. These systems can optionally also contain small amounts of a heavy metal salt.
• the copolymers are preferably prepared by solution polymerization in water, the monomers of group b) preferably being used in the salt form and the pH during the Polymerization between 4 and 10, preferably between 6 and 8 holds.
• a buffer such as, for example, disodium hydrogenphosphate.
• Water-soluble azo compounds such as 2,2 'azobis (2-methylpropionamidine) dihydrochloride, 2,2' azobis (4-methoxy-2,4,4-dimethylvalonitrile), 2,2'-azobis, are preferably used as the polymerization initiator -
• the compounds mentioned are mostly used in the form of aqueous solutions or dispersions, the lower concentration being determined by the amount of water acceptable in the (co) polymerization and the upper concentration being determined by the solubility of the compound in question in water.
• the concentration is generally 0.1 to 30% by weight, preferably 0.5 to 20% by weight, particularly preferably 1.0 to 10% by weight, based on the solution.
• the amount of initiators is generally 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the monomers to be (co) polymerized. Several different initiators can also be used in the (co) polymerization.
• Solvents or diluents can serve e.g. Water, alcohols, such as methanol, ethanol, n- or iso-propanol, n- or iso-butanol, or ketones, such as acetone, ethyl methyl ketone, diethyl ketone or iso-butyl methyl ketone.
• alcohols such as methanol, ethanol, n- or iso-propanol, n- or iso-butanol
• ketones such as acetone, ethyl methyl ketone, diethyl ketone or iso-butyl methyl ketone.
• the copolymerization is carried out in the presence of a regulator.
• Suitable regulators are, for example, secondary alcohols, such as isopropanol and sec. -Butanol, hydroxylamine, formic acid and mercapto compounds such as mercaptoethanol, mercaptopropanol, mercapto-butanol, thioglycolic acid, thiolactic acid, tert. -Butyl mercaptan, octyl mercaptan and dodecyl mercaptan.
• the regulators are usually used in amounts of 0.01 to 5% by weight, based on the monomers used.
• the polymerization can also take place in the presence of substantially larger amounts, for example in amounts of up to 80% by weight, based on the monomers. In these cases, the secondary alcohols are also solvents for the monomers.
• the (co) polymers thus obtainable have K values of 30 to 300, preferably 50 to 250. The K values are determined according to H. Fikentscher in 5% aqueous saline solution at pH 7, 25 ° C. and a polymer concentration of 0. 1% by weight.
• the (co) polymerization can also be carried out in another manner known per se to the person skilled in the art, e.g. as solution, precipitation, water-in-oil emulsion or reverse suspension polymerization. Solution polymerization is preferred.
• ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are used as surface-active compounds.
• (Co) Polymerization (Co) polymers of different molecular weights, which are characterized in this document with the help of the K values according to Fikentscher.
• (Co) polymers with a high K value e.g. above 80, are preferably prepared by (co) polymerizing the N-alkyl-N-vinylcarboxamide (I) in water.
• (Co) polymers with a high K value are also obtained, for example, by (co) polymerizing the monomers in the form of reverse suspension polymerization or by (co) polymerizing the monomers by the water-in-oil polymerization method.
• saturated hydrocarbons for example hexane, heptane, cyclohexane, decalin or aromatic hydrocarbons such as benzene, toluene, xylene and cumene
• the ratio of oil phase to aqueous phase in the reverse suspension polymerization is, for example, 10: 1 to 1:10.
• (Co) polymer with a low K value, e.g. below 80 is obtained if the (co) polymerization is carried out in the presence of polymerization regulators or in a solvent which regulates the (co) polymerization, e.g. Alcohols, such as methanol, ethanol, n- or iso-propanol, or ketones, such as acetone, ethyl methyl ketone, diethyl ketone or iso-butyl methyl ketone.
• Alcohols such as methanol, ethanol, n- or iso-propanol
• ketones such as acetone, ethyl methyl ketone, diethyl ketone or iso-butyl methyl ketone.
• (Co) polymers with low molecular weights and correspondingly low K values are also obtained using the customary methods, ie using larger amounts of polymerization initiator or using polymerization regulators or combinations of the measures mentioned.
• the molecular weight of the (co) polymers which can be used according to the invention is not restricted.
• (Co) polymers with K values between 30 and 110 are preferred, with K values between 40 and 90 being particularly preferred.
• the (co) polymers containing N-alkyl-N-vinylcarboxamides, for example of the formula (I) and especially N-vinylformamide, in copolymerized form can be used both in partially or completely cleaved and in uncleaved form.
• a degree of hydrolysis of between 0 and 30% is preferred, particularly preferably between 0 and 20% and very particularly preferably between 0 and 10%.
• the type of cleavage of the carboxylic acid or formyl group is not restricted, it can be carried out, for example, in the presence of acid or base; cleavage is preferred in the presence of bases, such as sodium hydroxide, potassium hydroxide, alkaline earth metal hydroxides, ammonia or amines.
• Partial hydrolysis e.g. of a (meth) acrylate and N-alkyl-N-vinylcarboxamides, for example of the formula (I) in copolymerized form, in copolymer, a photere (co) polymers are formed.
• Cationic copolymers of N-vinylformamide can be obtained particularly simply by hydrolytically cleaving homopolymers of N-vinylformamide with defined amounts of acid or base to the desired degree of hydrolysis, as described in EP-Bl 071 050.
• the resulting amino groups on the polymer chain are more or less protonated depending on the pH of the solution and thus give the polymer a more or less cationic character.
• the formyl group is split off in the hydrolysis at temperatures in the range from 20 to 200, preferably 40 to 180 ° C., in the presence of acids or bases.
• the hydrolysis in the presence of acids or bases is preferably carried out in the temperature range from 70 to 90 ° C.
• N-vinylformamide proceeds much faster than that of (co) polymers of other N-alkyl-N-vinylcarboxamides, such as B. of N-methyl-N-vinylformamide, and can therefore be carried out under gentler conditions, ie at lower temperatures and without a large excess of acids.
• the hydrolysis of the formyl groups of the poly-N-alkyl-N-vinylcarboxamide can also be carried out in an alkaline medium, e.g. in the pH range from 11 to 14. This pH is preferably adjusted by adding sodium hydroxide solution or potassium hydroxide solution. However, it is also possible to use ammonia, amines and / or alkaline earth metal bases. For the alkaline hydrolysis, 0.05 to 1.5, preferably 0.4 to 1.0 equivalents of a base are used.
• the cleavage can also be carried out at high temperatures, for example above 100 ° C, preferably 120 to 180 ° C, particularly preferably 140 to 160 ° C in the presence of a solvent, e.g. Water can be carried out without acid or base. This is preferably carried out under conditions above the critical point, for example with supercritical water.
• a solvent e.g. Water
• Water can be carried out without acid or base. This is preferably carried out under conditions above the critical point, for example with supercritical water.
• carboxylic acid group is split off from the poly-N-vinylcarboxylic acid amide in water in the presence of acids or bases; carboxylic acid, for example formic acid, or its salts is obtained as a by-product.
• solutions obtained can be used in the process according to the invention without further working up, but the hydrolysis or solvolysis products can also be separated off.
• the solutions obtained are treated, for example, with ion exchangers.
• the residue separated from the hydrolysis products can then be incorporated into the coating slips or used as an activator for the pretreatment.
• the molecular weight of the (co) polymers which can be used according to the invention is not restricted, but it should be adapted to the particular application process.
• the molecular weight should be relatively high, while it should be relatively low for application with a sprayer.
• the activators can be applied to the surface of the base paper or pre-coated paper by the process according to the invention by the methods customary for the surface treatment of paper in the paper industry. You can use known order units, such as. B. film presses, glue press various coating units with squeegees, blades or air brushes, or even spraying devices such as those used for. B. for the application of starch in EP-A 373 276 or for the application of coating slips by V. Nissinen, Kliblatt für Textilfabrikation, 2001, 11/12, S 794-806. The activators can also be applied when the paper is calendered by moistening.
• the activator is applied to the raw or pre-coated paper in one operation before the coating slip, which contains optical brighteners, is applied.
• the uncoated base paper that can be used for the pretreatment according to the invention generally has a water content of not more than 10% by weight, preferably not more than 8% by weight, particularly preferably between 3 and 8% by weight and in particular between 5 and 8% by weight.
• the pre-coated paper which can be used for the pretreatment according to the invention has generally already undergone one or two coating operations.
• the activators can be applied to the paper from aqueous solution or as a solution in methanol, ethanol, isopropanol, n-propanol, n-butanol, ethyl acetate, acetone or N-methylpyrrolidone, preferably from an aqueous solution, the Concentration should be chosen in such a way that the respective application process depends on eg the viscosity of the substance or solution to be applied can be optimally carried out.
• Usual concentrations are between 10 and 60% by weight.
• the activators can be applied to the paper as individual substances or in mixtures with one another.
• the activators can also be applied to the paper surface in a mixture with other paper chemicals that influence other paper properties.
• Such paper chemicals which can be applied to the paper together with the brightener activators according to the method according to the invention, are e.g. B. starch, cationic starch, other starch derivatives such as. B. hydroxyethyl, hydroxymethyl, methyl or ethyl starch ether, their polysaccharides such. B. guar or guar derivatives, carboxy-methyl, hydroxyethyl, hydroxymethyl, methyl or ethyl cellulose ether or surface conduction agent.
• the mass containing activators can also contain at least one pigment, at least one binder known per se and optionally other paper-typical auxiliaries (see below).
• optical brighteners are preferably only applied with a coating slip in a subsequent step (see below).
• the amount in which the activator is applied to the paper in accordance with the process according to the invention can vary within wide limits. In general, an amount of 0.05 g to 5 g should be applied per m 2 of paper, but an amount of 0.1 g to 3 g is preferred.
• the activators After applying the activators to the raw or pre-coated paper, e.g. by infrared emitters, to remove any solvent that may be present and, if desired, calendered (satinized) at a temperature between 15 and 100 ° C.
• the whiteness of the paper can often be increased further by adding a suitable activator for the optical brightener to the coating slip in addition to pretreating the paper.
• a suitable activator for the optical brightener to the coating slip in addition to pretreating the paper.
• This can be the same activator as was used for the pretreatment of the coating base paper or for one of the previous lines, but it can also be a different activator.
• Suitable activators are, for example, those already mentioned above.
• Preferred (co) polymers are those which contain N-vinylcarboxamides, e.g. the above N-vinyl-N-alkylcarboxamides of the formula (I), contained in copolymerized form.
• the (co) polymers containing N-vinylcarboxamides can be used both in partially or completely cleaved form and in uncleaved form.
• a degree of hydrolysis of between 0 and 30% is preferred, particularly preferably between 0 and 20% and very particularly preferably between 0 and 10%.
• the amount of activator in the coating slip will be chosen so that the viscosity of the coating slip is within the processing range. It is usually between 0.2 and 10% based on the pigment in the coating slip.
• the amount of (co) polymers which contain N-alkyl-N-vinylcarboxamides, for example of the formula (I), which can be added to the paper coating slip depends on the amount of brightener in the coating slip.
• optical brightener per 100 parts by weight of pigment are added to the coating slip.
• the same to five times the amount of the optical brightener is usually added to the coating slip, ie 0.2 to 10 parts by weight, preferably 0.5 to 8 and particularly preferably 1 to 5 parts by weight.
• the paper coating slip applied after the pretreatment according to the invention with an activator preferably contains at least one optical brightener.
• the paper coating slips also contain at least one white pigment and at least one binder.
• the paper coating slips can also contain further constituents known to the person skilled in the art. For example, Leveling agents, thickeners, wetting aids for the pigments etc.
• optical brighteners that can be used in connection with the method according to the invention are not restricted.
• brighteners such as those described in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Release, OPTICAL BRIGHTENERS - Chemistry of Technical Products can be used.
• Suitable optical brighteners belong, for example, to the group of distyrylbenzenes, for example cyano-substituted 1,4-distyrylbenzenes with cyano groups in positions 2 'and 3' '[CAS RegNr. 79026-03-2], or in position 2 'and 2' '[13001-38-2], 3' and 3 '' [36755-00-7], 3 'and 4 "[79026-02-1] as well as 4 'and 4 "
• distyrylbiphenyls for example 4,4'-di (2-sulfostyryl) biphenyl disodium salt [27344-41-8], 4,4'-di (3-sulfostyryl) biphenyl disodium salt [51119-63-2], 4,4 '-di (4-chloro-3-sulfostyryl) biphenyl disodium salt [42380-62-1], 4,4'-di (6-chloro-3-sulfostyryl) biphenyl disodium salt [60477-28-3], 4,4 'di (2-methoxystyryl) biphenyl [40470-68-6] or a 4, 4 '-di (styryl) biphenyl which has a group in position 2 on the styryl radical
• N-bis (hydroxyeth yl) amino and in addition to the anilino group a sulfonic acid group in position 3 (CAS RegNr. [12224-02-1]), N-bis (2-hydroxypropyl) amino and additionally on the anilino group a sulfonic acid group in position 4 (CAS Reg. No. [99549-42-5]), N-bis (hydroxyethyl) amino - and additionally on the anilino group a sulfonic acid group in position 4 (CAS Reg. [16470-24-9]), N-hydroxyethyl-N-methylamino and in addition on the anilino group a sulfonic acid group in position 4 (CAS RegNr.
• Stilbenyl-2H-triazoles for example stilbenyl-2H-naphtho [1,2-d] triazoles such as the sodium salt of 4- (2H-naphtho [1,2-d] triazol-2-yl) stilbene-2-sulfonic acid [6416 -68-8] or those in position n 6 carry a sulfonic acid on the naphthol ring and at position 2 of the stilbene structure [2583-80-4], or carry a cyano group on position 2 of the stilbene structure and a chlorine group on position 4 '[5516-20-1] or, for example, bis (1, 2,3-triazol-2-yl) stilbenes, such as, for example, 4,4′-bis (4-phenyl-1,2,3-triazol-2-yl) stilbene-2,2′-disulfonic acid dipotassium salt [52237-03 -3] or 4,4'-bis (4- (4- (4- (4- (4-4)
• Furans, benzo [b] furans and benzimidazoles such as e.g. Bis (benzo [b] furan-2-yl) biphenyls, for example sulfonated 4,4′-bis (benzo [b] furan-2-yl) biphenyls or cationic benzimidazoles, for example 2, 5-di (1-methyl-benzimidazole -2-yl) furan [4751-43-3], [72829-17-5], [74878-56-1],
• Bis (benzo [b] furan-2-yl) biphenyls for example sulfonated 4,4′-bis (benzo [b] furan-2-yl) biphenyls or cationic benzimidazoles, for example 2, 5-di (1-methyl-benzimidazole -2-yl) furan [4751-43-3], [72829-17-5], [74878-56-1]
• 1,3-diphenyl-2-pyrazolines e.g. 1- (4-Amidosulfonylphenyl) -3- (4-chlorophenyl) -2-pyrazoline [2744-49-2], [60650-43-3], [3656-22-2], [27441-70-9] , [32020-25-0], [61931-42-8] or [81209-71-4], as well as tertiary and quaternary amine salts of 1,3-diphenyl-2-pyrazoline derivatives, e.g.
• 4, 4'-Distyrylbiphenyl derivatives or stilbene derivatives which are substituted with up to 6, particularly preferably with 2, 4 or 6, sulfonic acid groups can preferably be used
• Tinopal® ® ® are Blankophor P and Blankophor PSG, further preferred are the Tinopal® brands from Ciba Specialty Chemicals, particularly preferred Tinopal® MC liquid, Tinopal® ABP-Z liquid, Tinopal®
• Leukophor® brands from Clariant AG, particularly preferably Leukophor® APN, UO, NS or SHR.
• the pigments that can be used in the coating slips are also not restricted.
• satin white calcium carbonate in ground or precipitated (precipitated) form
• barium sulfate in ground or precipitated form kaolin (clay)
• calcined clay talc
• silicates or organic pigments e.g. B. plastics in particle form
• binders ((co) polymeric binders) which can be used in the coating slips according to the invention are likewise not restricted.
• casein, starch, soy protein, carboxymethyl cellulose, alginate and / or polyvinyl alcohol or dispersions containing acrylic acid, acrylic acid ester, vinyl acetate and / or styrene in copolymerized form e.g. (Co) polymers of acrylic ester / styrene, styrene / butadiene or vinyl acetate can be used.
• the paper coating slips can also e.g. Contain dispersants.
• Suitable dispersants are polyanions, for example of polyphosphoric acids or of polyacrylic acids (polysalts), which are usually present in amounts of 0.1 to 3% by weight, based on the amount of pigment.
• the paper putties are usually aqueous paper coating slips.
• the water content can be adjusted depending on the desired viscosity or flow properties.
• the water content in the paper coating slip is usually set to 25 to 75% by weight, based on the total paper coating slip (including water).
• the processing of the coating slips is completely analogous to the processing of coating colors according to the prior art, e.g. according to "The Essential Guide to Aqueous Coating of Paper and Board", T.W.R. Dean (ed.), Published by the Paper Industry Technical Association (PITA), 1997, the "Guide to the Use of BASF Products in Paper and Cardboard Coating", BASF Aktiengesellschaft, D-6700 Ludwigshafen, Federal Republic of Germany, B 376 d, 09.77 or Ullmann's Encyclopedia of Technical Chemistry, 4th edition, vol. 17, pp. 603 ff.
• a thickener can be added.
• conventional organic and inorganic thickeners such as hydroxymethylcellulose or bentonite are suitable as thickeners.
• the components can be mixed in a known manner.
• the paper coating slips are suitable for coating paper or cardboard, for example.
• the paper coating slip can then be applied to the papers or cardboard to be coated using customary methods.
• the papers or cardboards coated with the paper coating slips according to the invention can be printed in customary processes, for example offset, letterpress or gravure printing processes or by digital printing processes, such as laser printing or inkjet printing processes.
• the method according to the invention makes it easier for the person skilled in the art to solve the difficult task of working out a recipe for a coating slip which, in addition to the many other components which influence the rheology and coating quality, conventionally also contains the brightener-activating activator.
• activators in addition to their brightening-enhancing effect, also change the properties of the coating slip and, through their interaction with the optical brighteners, even influence the rheological properties of the coating slip.
• the coating slips in addition to one or more pigments and one or more binders and the optical brightener, there are also thickeners, line hardeners, leveling agents, gloss agents, flow improvers, dispersants, wetting agents, lubricants, etc. The skilled person is grateful for any component whose properties he does not take into account and which he does not have to incorporate into the coating slip.
• Polymer solution has a degree of hydrolysis of 4.3% (enzymatic determination of the resulting formic acid).
• a commercially available wood-free coating base paper with the optical properties given in Table 1 was coated with 15 g / m 2 of a coating slip by means of a hand knife.
• the coating slip contained 33% water.
• the non-aqueous part existed
• the white R 457 of the paper was determined according to DIN 53 145, part 2.
• the CIE whiteness of the paper was measured according to ISO 2469.
• III paper coated with the coating slip which contains 2 parts of polyvinylformamide from Example D with a K value of 45.9 and a degree of hydrolysis of 5.4% as an activator.
• IV Paper according to the method of the invention, which has been pretreated with polyvinylformamide and is coated with a coating slip which contains no activator.
• V Paper according to the process of the invention, which has been pretreated with polyvinylformamide, but which additionally contains 2 parts of polyvinylformamide from Example D with a K value of 45.9 and a degree of hydrolysis of 5.4% as activator in the coating slip.
• Ciba Specialty Chemicals was used as an optical brightener.
• Example 2 The procedure was as in Example 1, with the difference that a 1,3,5-triazinyl derivative of 4,4'-diaminostilbene-2,2'-disulfonic acid with 6 sulfonic acid groups (Tin ⁇ pal SPP-Z liquid from Ciba Specialty Chemicals ) was used as an optical brightener, and that, if necessary, 1.5 parts of an unhydrolyzed polyvinylformamide from Example C, which acts as a rheology aid, binding agent improver and activator for the brightener, was added with the K value 45.9.
• Tin ⁇ pal SPP-Z liquid from Ciba Specialty Chemicals
• a commercially available wood-free coating base paper with the optical properties given in Table 1 was coated with 15 g / m 2 of a coating slip by means of a hand knife.
• the coating slip contains 33% water.
• the nonaqueous fraction consisted of 70 parts of calcium carbonate (Hydrocarb® 90, Pluss-Staufer AG), 30 parts of kaolin (Amazon ® 88, obtained through Kaolin in- ternational $), 8 parts of a polymer dispersion based on styrene and butadiene as a binder (Styronal® D 610, BASF Aktiengesellschaft), 0.5 parts of a 1, 3, 5-triazinyl derivative of 4, '-diaminostilben-2, 2' -disulfonic acid with 4 sulfonic acid groups (Tinopal ® ABP-Z liquid from Ciba Specialty ⁇ Chemicals) as an optical brightener and each 1.0 parts, 1.5 parts and 2.0 parts of the following activators:
• a 10 percent aqueous solution of a polyvinylformamide from Example D with a K value of 45.9 and a degree of hydrolysis of 5.4% (see above) was applied to the coating base paper before coating with the coating slip, using the doctor blade so that after drying 2 g / m 2 of the polyvinylformamide remained on the paper.
• a commercially available wood-free coating base paper with the optical properties given in Table 1 was coated with 15 g / m 2 of a coating slip by means of a hand knife.
• the coating slip contained 33% water.
• the non-aqueous part consisted of 70 parts of calcium carbonate (Hydrocarb® 90, Plüss-Staufer AG), 30 parts of kaolin (Amazon® 88, obtained from Kaolin International), 8 parts of a polymer dispersion based on styrene and butadiene as a binder (Styronal® D 610, BASF Aktiengesellschaft) and 0.5 parts of a 1, 3, 5-triazinyl derivative of 4, 4 '-diaminostilben-2, 2' -disulfonic acid with 6 sulfonic acid groups (Tinopal® SPP-Z liquid from Ciba Specialty Chemicals ) as an optical brightener.
• the coating base paper used was either not pretreated or various activators were applied to the coating base paper using the technique described in Example 1.
• the base papers were treated with the following activators before they were coated with the activator-free coating slip:
• Example 6 The procedure was as in Example 1, with the difference that a derivative of 4,4'-distyrylbiphenyl (Tinopal SK-B liquid from Ciba Specialty Chemicals) was used as an optical brightener and that 1.0 part, if necessary, was used as a rheological aid - Add agent, binding power improver and activator for the brightener acting unhydrolyzed polyvinylformamide from Example C with the K value 45.9 to the coating slip.
• Table 6 Table 6
• the method according to the invention is also advantageous if optical brighteners of a different chemical nature, e.g. B. based on derivatives of 4, 4 '-distyrylbiphenyl, can be used.
• a paper which had already been coated with a pigment-containing coating composition was provided with a topcoat by coating with a pigment-containing coating composition which contained 33% water.
• the non-aqueous portion of the coating slip consists of 70 parts of calcium carbonate - (Hydrocarb® 90 from Plüss-Staufer AG), 30 parts of kaolin (Amazon® 88, obtained from Kaolin International), 8 parts of a polymer dispersion based on styrene and Butadiene as a binder (Styronal® D 610 from BASF Aktiengesellschaft) and 0.5 part of a 1, 3, 5-triazinyl derivative of 4, 4 '-diamino-stilbene-2, 2' -disulfonic acid with 6 sulfonic acid groups ( Tinopal® SPP-Z liquid from Ciba Specialty Chemicals) as an optical brightener.
• the polymers specified in Table 7 are applied to the coated paper
• the paper provided with the top coat is dried, calendered and examined in accordance with the prior art.
• the white R 457 of the paper was determined according to DIN 53 145, part 2.
• the CIE whiteness of the paper was measured according to ISO 2469.
• the opacity was determined according to DIN 53146.

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