RU2802868C2 - Method for obtaining multilayer paper - Google Patents

Abstract

FIELD: paper industry.

SUBSTANCE: group of inventions can be used in the manufacture of multilayer packaging paper or cardboard. The process for producing dried multilayer paper includes producing first and second fibrous webs by dehydrating an aqueous fibrous suspension and spraying at least one side of the first and/or second fibrous web with a spray solution or spray suspension. The first and second fibrous webs are joined and then the resulting laminate is partially dehydrated by pressing. The partially dehydrated laminate is dried with heat to form a multilayer paper. Spray solution or spray suspension contains at least 75 wt% of water and water-soluble polymer P. Water-soluble polymer P is obtained by polymerization of the monomer of formula I,

where R ¹ means H or C1-C6 alkyl, and one or more ethylenically unsaturated monomers that are different from the monomer of formula I. A paper machine is also proposed.

EFFECT: group of inventions makes it possible to increase the strength of internal adhesion of layers in multilayer paper.

10 cl, 6 tbl

Description

The invention relates to a method for producing multilayer paper, including dehydration of two fibrous suspensions, thereby producing two fibrous webs, spraying an aqueous spray solution or sprayed suspension onto at least one fibrous web, joining two fibrous webs, thereby forming a layered material, dehydration of the layered material under presses into the partially dehydrated laminate and dehydrating the partially dehydrated laminate using heat to form a multi-layer paper, wherein the aqueous spray solution or spray suspension contains a water-soluble polymer P. Additional objects include the multi-layer paper produced by the process and a paper making machine, suitable for the method, which includes a spray device containing an aqueous spray solution or spray suspension containing polymer R.

Multilayer paper is produced from original mixtures of pulp or fiber mixtures with the same or different composition of the original composition by pressing together separate, still wet paper webs or layers of paper. An important indicator of the quality of multilayer packaging paper or cardboard is their strength. It is mainly determined by the internal adhesion of the materials used. Interlayer adhesion or interfacial adhesion between individual layers of paper may be a disadvantage. The trend towards using more recycled materials results in increasingly shorter paper fiber lengths and, as a result, significantly lower paper strength. In addition, when packaging in folding cartons, there is a tendency to use increasingly bulky fiber blends to increase flexural stiffness. Both trends increase the need for increased adhesion between layers.

To increase adhesion between layers, I often use adhesives based on starch or starch derivatives. For example, natural or modified starch based on wheat, corn, potato, tapioca is sprayed onto the paper fiber in the form of an aqueous solution. In the drying section of the paper machine, gelatinization occurs and thus hardening occurs. The use of natural starch is often characterized by the disadvantage that, due to its high viscosity, only a low solid content can be used in aqueous solution. Upon subsequent heat exposure, the starch composition may also become partially or completely and irreversibly brittle.

Patent EP 0953679 A describes polymers for increasing the strength of single- and multi-layer paper, which can be obtained by polymerizing at least 5 wt.% methacrylic acid, and which are applied, among other things, by spraying onto a layer of paper. Some examples describe spraying various terpolymers produced by the polymerization of acrylic acid, acrylamide and acrylonitrile onto a first fibrous web made from a fibrous slurry produced from old corrugated cardboard that is 86% moisture content. The second fiber web, which is also derived from old corrugated cardboard and has a moisture content of 96%, is then placed on the first spray-coated fiber web by pressing. The product is then dried and the strength of the two-ply paper is determined according to J-TAPPI Method No. 19-77. The decisive factor according to EP 0953679 A is the spraying of the polymers specified in the patent in dispersed form. In these examples, it was found that when the same polymers were sprayed in the form of a solution, which was obtained by increasing the pH value from 2.7 to 7.0, only approximately one third of the previous strength was achieved.

According to JP 2007-063682 A, polymers obtained by polymerization of N-vinylformamide followed by at least partial hydrolysis of formamide groups are used in combination with starch to improve adhesion between layers of multi-layer paper. The Examples section describes spraying various suspensions or solutions containing starch and/or a polymer solution onto a first fibrous web, which is derived from a fibrous slurry from old corrugated cardboard and has a moisture content of 82%. Then the second fiber web, also made from old corrugated cardboard from the fiber suspension and characterized by a moisture content of 92%, is combined with the first spray-coated fiber web by pressing. Then the resulting product is dried at 105°C and the strength of the resulting two-layer paper is measured according to J-TAPPI method No. 19-77. Also mentioned in the examples as polymers are polyallylamine and polymers obtained by polymerizing N-vinylformamide and then at least partially hydrolyzing the formamide groups.

The known method for producing multilayer paper still does not fully meet the requirements.

The present invention provides a basis for providing a multi-layer paper or paperboard that produces multi-layer paper or paperboard with improved strength. This technology must be easy to implement. Moreover, the strength must be maintained when subjected to high shear forces. The delamination of the layers should occur primarily along the original fiber fibers. Other desirable properties include maintaining strength when exposed to heat or humidity, during storage of the resulting multi-ply paper or board, or during further processing.

The authors propose a method for producing multilayer paper, which includes the following stages:

(A) dehydrating the first aqueous fibrous suspension, in which the solids content is from 0.1 wt.% to 6 wt.%, on the first screen, thereby obtaining a first fibrous web, in which the dry matter content is from 14 wt.% up to 25 wt.%,

(B) dehydrating a second aqueous fibrous suspension in which the solids content is from 0.1 wt.% to 6 wt.% on the second screen, thereby obtaining a second fibrous web in which the solids content is from 14 wt.% up to 25 wt.%,

(C) spraying the first fibrous web, the second fibrous web, or the first fibrous web and the second fibrous web on at least one side of the surface with a spray solution or spray suspension from a spray device, thereby producing at least one sprayed fibrous web, which contains the side of the surface with spraying,

(D) connecting the first fibrous web to a second fibrous web, at least one of the two webs being a sputtered fibrous web, such that at least one side of the sputtered surface forms a side of the surface in contact with the other fibrous web, and fibrous webs lie one above the other across their entire width, thereby creating a layered material,

(E) dehydrating the laminate by pressing, thereby forming a partially dehydrated laminate,

(F) dehydrating the partially dehydrated laminate by applying heat to form a dried laminate paper,

wherein the solution to be sprayed or the suspension to be sprayed contains

(s-a) water,

(c-c) at least one water-soluble polymer P, which can be obtained by polymerization

from 40 to 85 mol.% monomer of formula I

where R ¹ means H or C ₁ -C ₆ alkyl,

(ii) from 15 to 60 mol.% of one or more ethylenically unsaturated monomers, which differ from the monomer of formula I,

where the total amount of monomers (i) and (ii) is 100 mol.%,

and optionally by subsequent partial or complete hydrolysis of the monomer units of formula (I), which polymerize to form polymer P and to form primary amino groups or amidine groups,

where the proportion of water is at least 75 wt.% based on the sprayed solution or sprayed suspension.

Dry matter content means the ratio of the mass of the sample after drying to the mass of the sample before drying, and is expressed in mass percent (wt%). The dry matter content is preferably determined by drying at 105°C to constant weight. Drying occurs at 105°C (±2°C) in an oven to constant weight. In this case, constant mass is achieved if the value rounded to the first decimal place as a percentage no longer changes between 1 and 100 wt.% solids, and if the value rounded to the second decimal place as a percentage no longer changes changes when the dry matter content is from 0 to less than 1 wt.%. Drying is carried out at ambient pressure, possibly at 101.32 kPa, which is measured without correction for weather and altitude. In the Examples section you can find information on determining dry matter content in practice.

In step (A), the first aqueous fibrous suspension means a composition comprising water(a-a) and a first fibrous material (a-b) that contains cellulose fibers. Another name for fibrous suspension is cellulose pulp.

Mechanical and/or chemical methods can be used to obtain an aqueous fibrous suspension. For example, grinding an aqueous fiber suspension is a mechanical process to shorten the fibers and, in the case of cellulose fibers, also to defibrate the fibers. The dehydration ability of an aqueous fibrous suspension is also determined by the degree of grinding achieved. One method for measuring the fineness of a fiber slurry is to measure the degree of dehydration as recommended by Schopper Riegler in Schopper Riegler degree units (°SR).

Natural and/or regenerated fibers can be used as fibers. All fibers commonly used in the pulp and paper industry can be obtained from wood processing plants or from annual plants. Suitable annual plants for the production of fibrous materials are, for example, rice, wheat, sugar cane and kenaf. Pulp, such as from softwood or hardwood, includes, for example, defibrated wood, thermomechanical material (TMP), chemical-thermo-mechanical treated material (CTMP), pressure mill, semi-pulp, high yield pulp and refiner mechanical pulp (RMP). ). The reduction ratio of coarse mechanical pulp is typically 40-60°SR compared to standard pulp milling of 60-75°SR and fine milling of pulp cloth of 70-80°SR. Pulp, for example, from softwood or hardwood, includes pulp obtained by the chemical open sulfate, sulfite or soda method. The pulp may also exist in bleached or unbleached form. Preferred pulp is unbleached pulp, also called unbleached kraft pulp. Unground pulp is typically rated at 13-17°SR compared to low to medium pulp of 20-40°SR and fine pulp of 50-60°SR. Regenerated fibers can be obtained, for example, from waste paper. Waste paper may not necessarily be subjected to a decolorization process (removal of printing ink) before recycling. Mixed waste paper may typically exhibit a value of approximately 40° SR compared to waste paper from a bleaching process of approximately 60° SR. Regenerated fibers from waste paper can be used alone or mixed with other fibers, especially natural fibers.

An aqueous fibrous suspension can be obtained, for example, by recycling used paper or cardboard, for example, by mechanically treating waste paper in a pulper in a mixture with water until an aqueous fibrous suspension of the required consistency is formed. Another example of a combination of two fiber sources is the mixing of a virgin fiber slurry with recycled paper scrap, which is produced using the virgin fiber slurry.

In addition to water, the aqueous fibrous suspension may contain other components that may not necessarily have been added to the suspension knowingly or may have been present during the use of waste paper or paper used.

When a solids content of 2 wt.% to 4 wt.% is specified based on the aqueous fiber suspension (equivalent to a fiber concentration of approximately 20 to 40 g/l if fibers are present almost exclusively), it is generally intended to refer to the viscous material produced paper This material is generally distinguished from a non-viscous material having a solids content of from 0.1 wt.% to less than 2 wt.% based on the aqueous suspension of fibers (equivalent to a fiber concentration of about 1 to less than 20 g/l, if almost exclusively fibers present), in particular from 0.5 wt.% to 1.5 wt.% (from 5 to 15 g/l). The solids content or dry weight of an aqueous fiber suspension includes all components that are non-volatile or preferably non-volatile when determining the solids content when dried at 105°C to constant weight.

Another possible component of the first aqueous fiber suspension is (a-c) an organic polymer that is different from the fibers. The organic polymer (a-c) may be a neutral, cationic or anionic polymer.

A neutral organic polymer (a-c) may be an uncharged-neutral polymer because it does not contain polymer units with a functional group that is charged at at least pH 7. In this context, a functional group that is charged at at least pH 7 , means an atom or attached group of atoms that is covalently attached to the rest of the polymer unit. The functional group is permanently charged or acts on its own, that is, independently of other constituents of the polymer unit or other polymer units, in its uncharged form in pure water as an acid or base. The action of an acid results in the formation of a negative charge on the corresponding functional group of the polymer unit when deprotonated in the presence of a base. Such deprotonation can be carried out, for example, in the presence of NaOH, KOH or NH ₃ , which are usually used in aqueous solution, resulting in the formation of sodium, potassium or ammonium salts. The action of bases leads to the formation of a positive charge on the corresponding functional group of the polymer unit when protonated with an acid. Such formation can occur, for example, in the presence of HCl, H ₂ SO ₄ , H ₃ PO ₄ , HCOOH or H ₃ CCOOH, which are usually used in aqueous solution, which leads to the formation of the corresponding salts of chloride, hydrogen sulfate/sulfate, dihydrogen phosphate/hydrogen phosphate/ phosphate, formate or acetate. An example of a functional group with a permanent positive charge includes (-CH ₂ -) ₄ N+ (tetraalkylated nitrogen), such as in diallyldimethylammonium or 2-(N,N,N-trimethylammonium)ethyl acrylate. Examples of a functional group that results in the formation of negative charges in a polymer unit include -COOH (carboxylic acid), -SO ₂ OH (sulfonic acid), -PO(OH) ₂ (phosphonic acid), -O-SO ₂ OH (monoesterified sulfuric acid) or -O-PO(OH) ₂ (monoesterified phosphoric acid). Examples of a functional group that results in the formation of positive charges in a polymer unit include -CH ₂ -CH(NH ₂ )- or -CH ₂ -NH ₂ (primary and secondary basic amino group), (-CH ₂ -) ₂ NH (secondary and a basic amino group), (-CH ₂ -) ₃ N (tertiary and basic amino group) or (-) ₂ CH-N=CH-NH-CH(-) ₂ (basic amidine group, primarily in the form of a cyclic amidine).

Examples of the neutral organic polymer (a-c) that does not contain any polymer unit that carries a charge at at least pH 7 include polyacrylamide, acrylamide-acrylonitrile copolymer, polyvinyl alcohol, or vinyl alcohol-vinyl acetate copolymer.

The neutral organic polymer (a-c) may also be an amphoteric neutral polymer because it contains polymer units with a functional group that carries a positive charge at at least pH 7, and the number of all negative charges is equal to the number of all positive charges of the functional groups. An organic polymer in which the number of positive charges differs from the number of negative charges by less than 7 mol.% of the units is also considered an amphoteric neutral polymer, with 100 mol.% of the units being the number of all polymerized monomers used for the polymerization of organic polymers. For example, an organic polymer which is formed by the polymerization of 30 mol.% acrylic acid and 70 mol.% N-vinylformamide and in which half of the polymerized N-vinylformamide units are then hydrolyzed, and in which the difference in units between the functional groups -COOH and -CH ₂ - CH(NH ₂ ) - makes up 5 mol.%, is considered as an amphoteric-neutral polymer. In the case of polymerization of 10 mol.% itaconic acid (HOOC-CH ₂ -C(=CH ₂ )-COOH), 10 mol.% acrylic acid and 80 mol.% N-vinylformamide to form an organic polymer in which 44% of copolymerized units N-vinylformamide is hydrolyzed, the polymer is considered as an amphoteric-neutral polymer, in which the difference between the functional groups -COOH and -CH ₂ -CH(NH ₂ )- is 5 mol.%.

The cationic organic polymer (a-c) may be a purely cationic polymer, that is, it contains polymer units with a functional group that carries a positive charge at least at pH 7, but does not contain polymer units with a functional group that carries a negative charge at at least at pH 7. Examples of the purely cationic organic polymer (a-c) include polyallylamine, polydiallylamine, polydiallyldimethylammonium chloride, acrylamide-diallyldimethylammonium chloride copolymer, or acrylamide-2-(N,N,N)-trimethylammonium)ethyl acrylate chloride copolymer.

The cationic organic polymer (a-c) may also be an amphoteric cationic polymer, that is, it contains polymer units with a functional group that carries a positive charge at at least pH 7 and polymer units with a functional group that carries a negative charge at least least at pH 7, and the number of all positive charges is higher than the number of all negative charges in the composition of functional groups. An organic polymer in which the number of positive groups differs from the number of negative groups by 7 mol.% or more is considered an amphoteric cationic polymer, with 100 mol.% of the units being the number of all polymerized monomers used to prepare the organic polymers. For example, an organic polymer which is formed by the polymerization of 30 mol.% acrylic acid and 70 mol.% N-vinylformamide and in which 57% of the polymerized N-vinylformamide units are then hydrolyzed, and in which the difference in units between the functional groups -COOH and -CH ₂ -CH(NH ₂ )- is 10 mol.%, considered as an amphoteric cationic polymer.

The anionic organic polymer (a-c) may be a purely anionic polymer, that is, it contains polymer units with a functional group that carries a negative charge at least at pH 7, but does not contain polymer units with a functional group that carries a positive charge at at least at pH 7. Examples of the purely anionic organic polymer (a-c) include polyacrylic acid, styrene-n-butyl acrylate-acrylic acid copolymer, or acrylamide-acrylonitrile-acrylic acid copolymer.

The anionic organic polymer (a-c) may also be an amphoteric anionic polymer, that is, it contains polymer units with a functional group that carries a negative charge at at least pH 7 and polymer units with a functional group that carries a positive charge at least least at pH 7, and the number of all negative charges is higher than the number of all positive charges in the composition of functional groups. An organic polymer in which the number of negative groups differs from the number of positive groups by 7 mol% or more is considered an amphoteric anionic polymer, with 100 mol% of the units being the number of all polymerized monomers used to prepare the organic polymers. For example, an organic polymer which is formed by the polymerization of 30 mol.% acrylic acid and 70 mol.% N-vinylformamide and in which 29% of the polymerized N-vinylformamide units are then hydrolyzed, and in which the difference in units between the functional groups -COOH and -CH ₂ -CH(NH ₂ )- is 10 mol.%, considered as an amphoteric anionic polymer.

The organic polymer (a-c) may also be a linear, branched or cross-linked polymer. Cross-linking can occur, for example, by adding a cross-linking agent already during the polymerization of the starting monomers or by adding a cross-linking agent after polymerization, especially also shortly before adding the organic polymer (a-c) to the aqueous fiber suspension. For example, polyacrylamide can be cross-linked during polymerization by adding methylene bisacrylamide as a cross-linking agent to the acrylamide, or a cross-linking agent such as glyoxal can be added only after polymerization. If necessary, both types of crosslinking can be combined. Particular mention should be made of the cross-linked organic polymer with a high degree of cross-linking, which is usually obtained already during the polymerization of monomers. It is present in the first aqueous fibrous suspension in particulate form, primarily in the form of so-called organic microparticles.

The organic polymer (a-c) may also be a natural, modified natural or synthetic polymer. A natural organic polymer is usually obtained from a natural source using appropriate isolation steps, but excluding specific chemical modification and synthesis methods. An example of a natural organic polymer (a-c) is unmodified starch. None of the examples of natural organic polymer (a-c) is cellulose, which is the fibrous material (a-b). The modified natural organic polymer is modified at the chemical synthesis stage. An example of a modified natural polymer (a-c) is cationic starch. Synthetic organic polymer (a-c) is obtained by chemical synthesis from individual monomers. An example of a synthetic organic polymer (a-c) is polyacrylamide.

Organic polymer (a-c) as used herein also includes two or more different organic polymers. Accordingly, the organic polymer (a-c) is then separated, as an optional additional component of the first aqueous fiber suspension, into a first organic polymer (a-c-1), a second organic polymer (a-c-2), etc.

Another possible component of the first fiber suspension is filler (a-d). The filler (a-d) is an inorganic particle, primarily an inorganic pigment. Suitable inorganic pigments include all metal oxide, silicate and/or carbonate based pigments which are commonly used in the pulp and paper industry, especially pigments selected from the group consisting of calcium carbonate, in the form of ground lime, chalk, marble (GCC) or precipitated calcium carbonate (PCC), and talc, kaolin, bentonite, white satin, calcium sulfate, barium sulfate and titanium dioxide can also be used. The inorganic particle is also a colloidal solution of polysilicic acids, in which the silica particles are typically characterized by particle sizes ranging from 5 to 150 nm.

In this context, the filler (a-d) also includes two or more different fillers. Accordingly, the filler (a-d), as a possible other component of the first fiber suspension, can be divided into the first filler (a-d-1), the second filler (a-d-2), etc.

It is preferable to use inorganic pigments with an average particle size (volume average) of 10 μm, more preferably from 0.3 μm to 5 μm, especially up to 0.5 μm to 2 μm. In this context, the average particle size (volume average) of inorganic pigments and powder composition particles is generally determined by the quasi-elastic light scattering method (DIN-ISO 13320-1), for example using a Mastersizer 2000 from Malvern Instruments Ltd.

Another possible component of the first fiber suspension is another pulp and paper additive (a-e) which is different from the above components (a-b), (a-c) and (ad). Other additive (a-e) used in the pulp and paper industry includes, for example, a sizing agent, a water-soluble trivalent metal cation salt, a defoamer, a non-polymeric wet strength enhancing agent, a biocide, an optical brightener or a paper dye. Examples of the sizing agent include alkyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA) and resin-based adhesives. Examples of a water-soluble trivalent metal cation salt include aluminum(III) salts, especially AlCl ₃ such as AlCl ₃ ⋅6H ₂ O, Al ₂ (SO ₄ ) ₃ such as Al ₂ (SO ₄ ) ₃ ⋅18H ₂ O or KAl(SO ₄ ) ₂ ⋅12H ₂ O.

Other pulp and paper additive (a-e) in this context also includes two or more different other pulp and paper additives. Accordingly, the other additive used in pulp and paper production (a-e) can be divided into a first possible other component used in pulp and paper production of the first aqueous fiber suspension (a-e-1), a second possible other component used in pulp and paper production of the first aqueous fiber suspension (a-e-1), -e-2), etc.

In most cases, in the papermaking process, more than one organic polymer (a-c) and more than one filler (a-d) are added to the first aqueous fiber suspension. In the case of an organic polymer (a-c), it is used, for example, to influence the technological properties of the paper production process itself or the technological properties of the resulting paper. Retaining agents, dehydrating agents, wet strength agents or dry strength agents are also used.

Examples of retention agents are cationic, amphoteric or anionic polymers (a-c). Examples include anionic polyacrylamide, cationic polyacrylamide, cationic starch, cationic polyethylenimine or cationic polyvinylamine. The retention agent can be, for example, a filler (a-d), which is an anionic microparticle, especially colloidal silicic acid or bentonite. Combinations of the examples mentioned above can also be used. As a combination, mention should first be made of a binary system, which consists of a cationic polymer with an anionic microparticle or an anionic polymer with a cationic microparticle. The preferred retention agent is a synthetic organic polymer (a-c) or a dual system. In the case of a dual system, a cationic first organic polymer (ac-1) already exists as a retention agent in combination with a first filler (ad-1), for example a suitable bentonite, and a second filler (ad-2), calcium carbonate.

The first fibrous suspension preferably contains an organic polymer (a-c) which is a synthetic organic polymer. Preferred is the organic polymer (a-c) which is polyacrylamide. The preferred organic polymer (a-c) is cationic polyacrylamide. First of all, the organic polymer (a-c) which is a cationic polyacrylamide and acts as a holding agent is preferred.

The mass amount of the organic polymer (a-c) is preferably from 0.001 mass% to 0.2 mass% based on the mass of the first fibrous material (a-b) in the first fibrous suspension. The mass amount of the first fibrous material (a-b) refers to the solids content of the first fibrous material (a-b), and the mass amount of the organic polymer (a-c) refers to the solids content of the organic polymer (a-c). The organic polymer solids content (a-c) is determined from the organic polymer sample (a-c) after drying the sample in a forced air oven at 140° C. for 120 minutes. For example, in the case of an aqueous solution, suspension or emulsion of a polymer, the sample is placed in a metal substrate to dry. Drying is carried out at ambient pressure, if possible at 101.32 kPa, and the pressure is set without correction for variations due to weather and altitude. The mass amount of the organic polymer (a-c) is more preferably from 0.005 wt% to 0.1 wt% based on the weight of the first fibrous material (a-c) in the first fibrous suspension, especially preferably from 0.01 wt% to 0.08 wt%, most preferably from 0.02 wt% to 0.06 wt% and especially preferably from 0.3 wt% to 0.05%.

The mass amount of the organic polymer (a-c), which is a cationic polyacrylamide, is preferably from 0.001 mass% to 0.2 mass% based on the mass of the first fibrous material (a-b) in the first fibrous suspension.

The anionic organic polymer is preferably not added to the first fiber suspension.

Examples of the dry strength increasing agent include a synthetic organic polymer (a-c), such as, for example, polyvinylamine, polyethylenimine, polyacrylamide or glyoxylated polyacrylamine, or a natural organic polymer (a-c), such as unmodified starch.

The solids content of the first aqueous fiber suspension is preferably 0.11 wt% to 5 wt%, highly preferably 0.12 wt% to 4 wt%, particularly preferably 0.13 wt%. up to 3 wt.%, 2 wt.%, 1 wt.%, 0.6 wt.% or 0.35 wt.% as an upper limit, and most preferably from 0.14 wt.% to 0.30 wt. %.

The first mesh, which is characterized by an upper part of the first mesh and a lower part of the first mesh, has mesh cells as openings. The first aqueous fiber suspension is applied to the mesh through a headbox. The headbox ensures uniform application of the original fiber slurry across the entire width of the mesh, excluding screen meshes or other projections associated with the material, and a certain radial bend in the case of a ring mesh. This device makes it possible to obtain a uniformly thin and, if possible, homogeneous fibrous web. After applying the first fiber slurry, the water portions (a-a) of the first fiber slurry pass through the mesh cells, whereupon sheets are formed on the top of the first mesh and the first fiber web is formed. The fibrous web obtained in this way is flat, that is, it has a very small height in relation to its length and width. The fibrous material of the fibrous material suspension, as well as possible other components that are present in the final paper, such as filler, are ideally completely or at least substantially retained in the resulting fibrous web. Possible additional components of the fiber slurry that are added to maintain retention of other components, to maintain dehydration of the fiber slurry, or to support the formation of a uniform web, such as an organic polymer, have an effect in this process. In most cases, these possible additional components of the fibrous suspension are completely, or at least substantially, retained in the resulting fibrous material. The dry portion of the fibrous web, which determines the solids content of the fibrous web, contains the retained components of the fibrous material, possible other components that must be present in the final paper, and possible additional components. Depending on their holding properties, these components are, for example, the aforementioned fibers, organic polymers, fillers and other additives used in pulp and paper production. Upon completion of step (A), the fibrous web is sufficiently hard to be separated from the mesh.

The mesh contains, for example, metal or plastic cells. Preferably the mesh is an endless mesh. After the resulting fiber web is separated from the endless mesh, the endless mesh is moved back to the material application section, where a new fiber slurry is applied to the moving endless mesh. First of all, a mesh that moves around several rolls is preferred.

Known types of endless screen sieves are the flat mesh screen, the double forming screen with an endless bottom screen and one of its additional endless top screens, the cylindrical screen and cylindrical forming devices. A flat mesh sieve is preferred.

Dehydration of the fiber suspension on the top grid can be maintained by applying a vacuum from the bottom side of the grid. Negative pressure means a pressure lower than the pressure at the top of the grid, which corresponds to, for example, ambient pressure.

The solids content of the first fibrous web is preferably from 15 wt% to 24 wt%, more preferably from 16 wt% to 23 wt%, most preferably from 17 wt% to 22 wt%, especially preferably from 17.5 wt.% to 22 wt.% and especially preferably from 18 wt.% to 21 wt.%.

The mass of a square meter of fibrous web is in this context defined as the mass of components per square meter of fibrous web that is retained after drying, preferably retained as a constant mass, during the determination of solids content after drying at a drying temperature of 105°C. Preferred weight per square meter of fibrous web is from 20 to 120 g/m ² . The sum of all masses per square meter of fibrous webs is not the density of the dried multi-layer paper ultimately obtained from them, since at least one of the layers in the composition of the fibrous web will be sprayed with a slight increase in density, when dehydrated by pressing and strictly speaking when dehydrated on a heated cylinder, the laminate may again lose some of the above components after low-density drying or, at the entry of said dehydration or other steps, the dried laminate or its wet products from previous stages may be stretched or compressed. In the latter case, one square meter of fiber web will no longer correspond to one square meter of dried multi-ply paper. On the other hand, the approximately square meter weight of the flat first fibrous web may correspond to the proportion of the layer produced from that fibrous web in the subsequent process in the total weight of the dried multi-ply paper. The weight per square meter of the first fibrous web is, for example, from 30 to 100 g/ ^m2 , from 30 to 60 g/ ^m2 , from 65 to 105 g/ ^m2 , from 35 to 50 g/m2 ^or from 70 to 90 g/ ^m2 .

In step (B), the second aqueous fibrous suspension means a composition comprising water (b-a) and a second fibrous material (b-c) that contains cellulose fibers. The explanations and preferences for step (A), mutatis mutandis, can be applied to step (B), that is, using an organic polymer (b-c) or a first organic polymer (b-c-1) and a second organic polymer (b-c-2) and etc., respectively, we mean filler (b-d) or first filler (b-d-l) and second filler (b-d-2), etc., another additive used in pulp and paper production (b-e) or first used a pulp and paper additive (b-e-1) and a second pulp and paper additive (b-e-2), as well as a second grid that includes an upper portion of the second grid and a lower portion of the second grid, a second fiber web, and a pulp square meter of second fiber web.

The second fibrous material (bb) preferably means the same material as the first fibrous material (a-b). The organic polymer (b-c) preferably means the same as the organic polymer (a-c), or the first organic polymer (bc-1) means the same polymer as the first organic polymer (a-c-1); the first organic polymer (bc-1) most preferably means the same polymer similar to the first organic polymer (a-c-1) and the second organic polymer (bc-2) similar to the second organic polymer (a-c-2). The second organic polymer (b-c) is preferably contained in the same amount by weight, based on the second fibrous material (bb), as the first organic polymer (a-c) based on the first fibrous material (a-b). The mass amount of the organic polymer (a-c), which is a cationic polyacrylamide, is preferably from 0.001 wt.% to 0.2 wt.% based on the weight of the first fibrous material (a-b) in the first fibrous suspension, and the weight of the organic polymer (b-c), which is a cationic polyacrylamide, is from 0.001 wt.% to 0.2 wt.% based on the weight of the second fibrous material (bb) in the second fibrous suspension. The filler (bd) is preferably the same filler similar to the filler (ad), or the first filler (bd-1) is the same first filler similar to the first filler (a-d-1), and the first filler (bd-1 ) is most preferably the same first filler, similar to the first filler (a-d-1), and a second filler (bd-2), similar to the second filler (ad-2). The other pulp-and-paper additive (b-e) is preferably the same additive as the other pulp-and-paper additive (a-e), or the first different pulp-and-paper additive (b-e-1) is the same another first additive similar to the first additive used in pulp and paper production (a-e-1), especially preferably the first other additive used in pulp and paper production (b-e-1) is the same first different additive similar to the first additive used in pulp and paper production (a-e-1), and the second different pulp additive (b-e-2) is the same additive as the second different pulp additive (a-e-2). The composition of the second fibrous suspension is preferably the same composition as the composition of the first fibrous suspension. The weight per square meter of the first fibrous web is preferably higher than the weight per square meter of the second fibrous web, particularly preferably the weight per square meter of the first fibrous web is from 65 to 105 g/m ² and the weight per square meter of the second fibrous web is from 30 to 60 g/m ² .

The organic polymer (a-c) is preferably added to the first aqueous fibrous suspension containing water (a-a) and the first fibrous material (a-b) before dehydration in step (A) as a retaining agent, and to the second aqueous fibrous suspension containing water (b-a) and a second fibrous material (b-b), an organic polymer (b-c) is added as a retaining agent before dehydration in step (B). The amount of added polymer (a-c) is particularly preferably from 0.001 wt.% to 0.2 wt.% based on the weight of the first fibrous material (a-b), and the amount of added organic polymer (b-c) is from 0.001 wt. .% to 0.2 wt.% based on the second fibrous material (b-b). The amount of added polymer (a-c) is primarily preferably from 0.020 mass% to 0.15 mass%, and the amount of polymer added (b-c) is from 0.0020 mass% to 0.15 mass%. These amounts are particularly preferred if the polymer (a-c) and polymer (b-c) are a cationic polymer, and particularly preferably a cationic polyacrylamide.

In step (A), the first fiber slurry is preferably applied to the top side of the first grid and dehydration is maintained by applying negative pressure to the bottom side of the first grid, and in step (B), the second fibrous suspension is preferably applied to the top side of the second grid and dehydration is maintained at by applying negative pressure to the bottom side of the second grate, or in step (A), the first fiber slurry is preferably applied to the top side of the first grate and dehydration by applying negative pressure to the bottom side of the first grate, and in step (B), the second fibrous suspension is applied to the upper side of the second grid and dehydration is maintained by applying negative pressure to the lower side of the second grid. In step (A), the first fiber slurry is preferably applied to the top side of the first grate and dehydration is maintained by applying negative pressure to the bottom side of the first grate, and in step (B), the second fibrous suspension is applied to the top side of the second grate and dehydration is maintained by applying vacuum onto the underside of the second grid.

In step (C), at least one surface side of the first fibrous web or the second fibrous web is sprayed with a spray solution or spray suspension. In this case, at least one fibrous web is obtained with a coating applied to the surface side. The first fibrous web and the second fibrous web are preferably sprayed, most preferably simultaneously, and most preferably both fibrous webs are sprayed from a spray device.

The spraying in step (C) of the spray solution or spray suspension is preferably carried out from a spray device. The spray nozzle contains, for example, one or more nozzles. The spray solution or spray suspension is sprayed from a nozzle or nozzles onto the surface side of the fibrous web, which is intended for spraying. The spray solution or spray suspension is supplied at an excess pressure relative to ambient pressure, for example from 0.5 to 15 bar, preferably from 0.5 to 4.5 bar and most preferably from 0.8 to 2.5 bar. Excessive pressure is created shortly before exiting the nozzle. A container for storing the spray solution or spray suspension may be part of the spray device.

In step (D), joining the first fibrous web to the second fibrous web forms a laminate. The flat side of the first fibrous web is in continuous contact with the flat side of the second fibrous web. At least one of the two sides of the surface is the coated side. As a result of the connection, the sides of the surfaces are in contact at least enough to provide weak adhesion to each other. The fibrous webs are arranged or connected in such a way that the entire width of the fibrous webs are located one above the other or the fibrous webs cover each other over the entire surface. The connection corresponds to complete alignment of the first fibrous web and the second fibrous web. From the point of view of space and time, the registration occurs, for example, almost immediately before the pressing stage (E). In step (C), the first fibrous web and the second fibrous web are preferably sprayed to form at least two sprayed fibrous webs, and in step (D), the first fibrous web is bonded to the second fibrous web such that the surface side of the first the sputtered fibrous web is a surface contact side of the second fibrous web, and the surface side of the second sputtered fibrous web forms a surface contact side of the first fibrous web.

In step (E), the laminate is compressed, resulting in additional dehydration and a corresponding increase in dry matter content. In step (E), first the laminate obtained in step (C) reaches the so-called forming section. During molding, dehydration occurs after mechanical pressure is applied to the laminate. Removing water by mechanical pressure is more energy efficient than removing water by heating or drying. When the laminate is applied to a water-absorbent tape, such as a felt-like fabric, dehydration is maintained by absorbing the squeezed-out water. A roller may be used to apply pressure to the laminate. First of all, it is suitable to pass the laminate material through two rollers in order to ensure, if necessary, pressing against the water-absorbing tape. The surface of the roller consists, for example, of steel, granite or vulcanized rubber. The surface of the roller may be coated with water-absorbing material. Water-absorbing materials are characterized by high absorbency (absorption) capacity, porosity, strength and elasticity. After contact with the laminate, the water-absorbing materials are ideally dehydrated again on the side opposite the laminate, for example using a rubber roller.

Upon completion of stage (E), a partially dehydrated network structure is created that is sufficiently solid to be guided to the next stage without mechanical support. The partially dehydrated laminate is characterized, for example, by a dry matter content of from 35 wt.% to 65 wt.%. The solids content of the partially dehydrated laminate is preferably 37% by weight to 60% by weight, most preferably 38% by weight to 55% by weight, particularly preferably 39% by weight to 53% by weight, even more preferably 39% by weight to 53% by weight. preferably from 40 wt.% to 52 wt.%.

In step (A), the partially dehydrated laminate obtained in step (E) is further dehydrated by heating, and at the end of step (F), a dried laminate paper is obtained. Heating of the partially dehydrated laminate is accomplished, for example, by heated cylinders through which the partially dehydrated laminate is passed, by IR emitters, by warm air passed over the partially dehydrated laminate, or by using two or all three measures. The heat supply is preferably carried out using heated cylinders. The cylinders can also be heated with electricity or steam. Typical cylinder temperatures range from 120°C to 160°C. You can use cylinders with a surface coating that will improve the surface quality of the dried multi-ply paper. The dried multi-layer paper has the highest strength compared to the first fibrous web or the combined strength of all fibrous webs, laminate or partially dehydrated laminate. It is believed that starting from a solids content of 80 wt.%, the hydroxyl groups of the cellulose fibers increasingly form hydrogen bonds, which contribute to the previous felting of the fibers. A measure of the strength of dried multi-layer paper is, for example, the internal bond strength.

Dried multi-layer paper in this context is defined as a sheet material that is characterized by a density, that is, a weight of 1 m ² of dry paper up to 600 g/m ² . The resulting paper in a narrower sense is usually used for densities up to 225 g/m ² , while the resulting board is used for densities from 150 g/m ² .

The density of the dried multi-ply paper is preferably from 20 to 400 g/ ^m2 , most preferably from 40 to 280 g/ ^m2 , especially preferably from 60 to 200 g/ ^m2 , even more preferably from 80 to 160 g/ ^m2 , particularly preferably from 90 to 140 g/m ² and even more particularly preferably from 100 to 130 g/m ² .

The dried multi-layer paper preferably contains two, three or four layers, more preferably two or three layers, particularly preferably two layers. In the case of two layers, only one first fibrous web and one second fibrous web are present in the process. In the case of three layers, an additional fibrous web is present as the third fibrous web, and in the case of four layers, another additional fibrous web is present as the fourth fibrous web. The third and optionally fourth fibrous web, whether or not spray-coated, are attached to the laminate of the first fibrous web and the second fibrous web. This is followed by additional dehydration in steps (E) and (F).

The first fibrous web and the second fibrous web each contribute to the density of the dried laminate paper. These contributions may be the same or different. The contributions correspond approximately to the masses per square meter of the corresponding fiber web. The contribution of the first fibrous web to the density of the dried laminate paper is preferably greater than the contribution of the second fibrous web, more preferably the ratio is 3 or more parts of the first fibrous web to 2 or less parts of the second fibrous web. Most preferably, the ratio is 3 or more parts of the first fibrous web to 2 or less parts of the second fibrous web, or 4 parts of the first fibrous web to 1 or less parts of the second fibrous web.

The dry matter content of the dried multi-layer paper is, for example, at least 88% by weight. The solids content of the dried multi-layer paper is preferably from 89% by weight to 100% by weight, most preferably from 90% by weight to 98% by weight, especially preferably from 91% by weight to 96% by weight, particularly preferably from 92 wt.% to 95 wt.% and even more preferably from 93 wt.% to 94 wt.%.

The method for producing multi-layer paper may include other steps. For example, after step (F), a calendering step of the dried multi-ply paper can be carried out.

Polymer P is water-soluble if its solubility in water under normal conditions (20°C, 1013 mbar) and at pH 7.0 is at least 5 wt.%, preferably at least 10 wt.%. Mass% corresponds to the content of solid polymer P. The fixed content of polymer P is determined after it is obtained in the form of an aqueous solution of the polymer. A sample of the polymer solution is dried on a sheet metal support in a forced air oven at 140°C for 120 minutes. Drying is carried out at ambient pressure, possibly at 101.32 kPa, which is measured without correction for variations due to weather and altitude.

Spray solution in this context means polymer P dissolved in water. If another liquid is present that does not mix well with the water to be dissolved, this mixture is also called spray solution in this context. Conversely, there are no solid particles in the spray solution. There are also no solid particles with a colloidal particle size, that is, <10 ^-5 cm. The sprayable dispersion is a solution of polymer P in water intended for dissolution, in which there are additionally water-insoluble solid particles. If there is another liquid present that does not mix well with the water intended to be dissolved, the mixture is also called a spray suspension in this context. In this case, the temperature is 23°C and the ambient pressure is approximately 101.32 kPa.

The pH value of the sprayed solution or sprayed suspension is 5.5 or more. The pH value of the spray solution or suspension is more preferably from 5.8 to 12, particularly preferably from 6.2 to 11, even more preferably from 6.4 to 10, most preferably from 6.8 to 9, and especially preferably from 7 .2 to 8.8.

Due to the high water content, the density of the spray solution or spray suspension can be assumed to be approximately 1 g/cm ³ .

The sprayable solution or sprayable suspension preferably contains

(s-a) water,

(c-c) at least one polymer P,

(c-c) optionally another connecting layer that differs from polymer P,

(c-d) an optional sprayable adjuvant, which is different from the polymer P and other connecting layer,

where the water content (c-a) is at least 80 wt.% based on the weight of the sprayed solution or sprayed suspension.

The spray solution or spray suspension preferably contains at least 85 wt% to 99.99 wt% water (c-a) based on the total weight of the spray solution or spray suspension, most preferably at least 95 wt% to 99.95 wt%, particularly preferably 98 wt% to 99.9 wt% water and even more preferably 99 wt% to 99.7 wt% water.

The spray solution or spray suspension preferably contains from 0.01 wt.% to less than 15 wt.% of polymer P (c-b) based on the total weight of the spray solution or spray suspension, more preferably from 0.05 wt.% to less 5 wt% of polymer P, particularly preferably from 0.1 wt% to less than 2 wt% of polymer P, even more preferably from 0.15 wt% to less than 1 wt% of polymer P and most preferably from 0. 3 wt.% to less than 0.8 wt.% of polymer R. The mass of polymer R in the spray solution or spray suspension corresponds to the solid content of polymer R.

The additional connecting layer (c-c), which is different from the polymer P, is, for example, an organic polymer. Preferred are natural polysaccharide, modified polysaccharide, protein or polyvinyl alcohol. It is also possible to use a mixture of several connecting layers. A natural polysaccharide is, for example, natural starch or guar flour. The modified polysaccharide is, for example, chemically modified starch or cellulose ether. The protein is, for example, gluten or casein. For example, a cellulose ether is carboxymethylcellulose.

An example of natural starch is starch from corn, wheat, oats, barley, rice, millet, potato, pea, cassava, black millet or sago. In this context, degraded starch is characterized by a reduced weight average molecular weight compared to natural starch. Starch can be degraded by enzymatic, oxidative methods, under the action of acid or alkali. Enzymatic degradation or degradation by acids or alkalis in the presence of water by hydrolysis results in increased levels of oligosaccharides or dextrins. Some types of degraded starches are produced by companies. Starch degradation is a chemical process. Chemical modification is the introduction of functional groups into a natural starch molecule through the covalent addition of a chemical group or the breaking of covalent bonds in the starch. Chemically modified starch can be obtained, for example, under the conditions of formation of esters or ethers of natural starch (esterification) followed by degradation of starch. The preparation of esters is carried out in the presence of inorganic or organic acid. For example, an acid anhydride or acid chloride is used as a reagent. A typical procedure for preparing starch ethers involves treating the starch with an organic reagent containing a reactive halogen atom, epoxy group or sulfate group in an alkaline aqueous reaction mixture. Known types of starch ethers include alkyl ethers, uncharged hydroxyalkyl ethers, carboxylic acid alkyl ethers or 3-methylammonium-2-hydroxypropyl ether. The chemically modified starch may be, for example, phosphatized degraded starch or acetylated degraded starch. Chemically modified starch, for example, may be a neutral, anionic or cationic compound.

The additional connecting layer (c-c) may be a neutral, anionic or cationic compound. Neutral compounds are divided into uncharged neutral and amphoteric neutral. The difference is consistent with the definitions presented for organic polymer (a-c). An uncharged neutral compound means that at pH 7 there are no charged atoms or functional groups. An amphoteric neutral compound means that at pH 7 there are both atoms or functional groups with a positive charge and atoms or functional groups with a negative charge, the total charges differing by less than 7 mol.%, and all of them are charged at 100 mol.%. . Cationic compounds themselves are divided into purely cationic and amphoteric-cationic. Anionic compounds themselves are divided into purely anionic and amphoteric-anionic. Most preferred is another connecting layer (c-c) that is uncharged neutral, amphoteric neutral, purely anionic, amphoteric anionic, or amphoteric. First of all, another connecting layer (c-c) that is neutral or anionic is preferred. Most preferred is the other connecting layer (c-c), which is uncharged neutral or purely anionic. Most preferably, the other connecting layer (c-c) is uncharged neutral.

The spray solution or spray suspension preferably contains from 0 wt.% to 15 wt.% of the other connecting layer (c-c) based on the total weight of the spray solution or spray suspension. Most preferably, the amount of the other connecting layer (c-c) is from 0.05 wt% to less than 5 wt% of the other connecting layer (c-c), especially preferably from 0.1 wt% to less than 2 wt%. another connecting layer (c-c), even more preferably from 0.15 wt.% to less than 1 wt.% of the other connecting layer (c-c) and especially preferably from 0.3 wt.% to less than 0.8 wt. % of other connective layer (s-s).

The weight amount of the other tie layer (c-c) is preferably equal to or lower than the weight amount of the polymer P (c-b) defined as the solids content of the polymer P (c-b) and the solids content of the other tie layer ( c-c) in a spray solution or spray suspension, which is preferably equal to or lower than half the mass amount of polymer P (c-b), more preferably equal to or lower than one third the mass amount of polymer P (c-b), and above the total is preferably equal to or lower than one quarter of the mass amount of polymer P (c-b).

The sprayable adjuvant (c-d), which is different from the polymer P and the other connecting layer, is, for example, a viscosity regulator, a pH regulator, an antifoam or a biocide.

The spray solution or spray suspension preferably does not contain another connecting layer (c-c), which is cationic starch. The sprayable solution or sprayable suspension preferably does not contain another connecting layer (c-c), which is starch. The sprayable solution or sprayable suspension preferably does not contain another connecting layer (c-c) which is purely cationic. The solution to be sprayed or the suspension to be sprayed particularly preferably does not contain another connecting layer (c-c) which is cationic. The sprayable solution or sprayable suspension preferably does not first of all contain another connecting layer (c-c) which is an organic polymer and different from the polymer P.

The sprayable auxiliary agent (c-d), which differs from the polymer P and from the other connecting layer, is, for example, a viscosity regulator, defoamer or biocide.

The spray solution or spray suspension preferably contains from 0 wt.% to less than 2 wt.% spray (c-d) based on the total weight of the spray solution or spray suspension. The amount of sputtering (c-d) is most preferably from 0.001 wt.% to less than 1 wt.% sputtering, especially preferably from 0.005 wt.% to less than 0.8 wt.% sputtering (c-d) and especially preferably from 0.01 wt. % to less than 0.5 wt.% sputtering (c-d).

The mass amount of the other spray auxiliary (c-d) is preferably equal to or lower than the mass amount of polymer P (c-b), defined as the solids content of the polymer P (c-b), and in the spray solution or spray suspension, which is preferably equal to or less than one twentieth by weight of polymer P (c-b), more preferably equal to or lower than one thirtieth by weight of polymer P (c-b), and especially preferably equal to or lower than one fortieth by weight of polymer P(c-b).

The sprayable solution or sprayable suspension preferably does not contain polydiallyldimethylammonium chloride or pentaethylenehexamine which is substituted with an alkyl group or arylalkyl group containing at least 5 carbon atoms. The sprayable solution or sprayable suspension preferably contains preferably does not contain a homopolymer or copolymer of protonated or quaternized dialkylaminoalkyl acrylate, homopolymer or copolymer of protonated or quaternized dialkylaminoalkyl methacrylate, homopolymer or copolymer of protonated or quaternized dialkylaminoalkylacrylamide, homopolymer or copolymer of proton protonated or quaternized dialkylaminoalkylamyl acrylate, homopolymer or copolymer of protonated or quaternized diallyldimethylammonium chloride or pentaethylenehexamine which is substituted with an alkyl group or an arylalkyl group containing at least 5 carbon atoms.

The sprayable solution or sprayable suspension preferably does not contain a filler as defined above for filler (a-d).

The spray solution preferably contains

(s-a) water,

(c-b) water-soluble polymer P,

(c-c) another connecting layer that differs from polymer P,

(c-d) spray auxiliary agent,

wherein the water content (c-a) is at least 80 wt.% based on the weight of the sprayed solution or sprayed suspension, and the content of the sprayed auxiliary agent (c-d) is from 0 wt.% to less than 2 wt.% based on the mass spray solution or spray suspension.

The applied amount of spray solution or spray suspension is preferably from 0.05 g/m ² to 5 g/m ² based on the solids content of the spray solution or spray suspension and based on the area sprayed, most preferably from 0.1 g /m ² to 3 g/m ² , especially preferably from 0.3 g/m ² to 1.5 g/m ² , especially preferably from 0.4 g/m ² to 1.0 g/m ² , more more preferably 0.5 g/ ^m2 to 0.8 g/ ^m2 .

To polymerize monomers (i) and (ii) to obtain polymer P, solution, precipitation, suspension or emulsion polymerization can be used. Preferred is polymerization in an aqueous environment. Suitable aqueous media are water and mixtures of water and at least one water-miscible solvent, for example alcohol. Examples of alcohol include methanol, ethanol or n-propanol. Radical polymerization is carried out, for example, using radical polymerization initiators, such as peroxides, hydroperoxides, so-called redox catalysts or azo compounds, which decompose to form radicals. The polymerization is carried out, for example, with water used as a solvent or a mixture containing water in the temperature range from 30°C to 140°C, and the polymerization can be carried out at ambient pressure, at reduced or elevated pressure. As the water-soluble polymerization initiator, a solution polymerization initiator such as 2,2'-azobis(2-methylpropionamidine) dichloride is preferably selected.

When polymerizing monomers (i) and (ii) to form polymer P, regulators can be added to the reaction mixture. Typically, 0.001 to 5 mol% is used, based on the total amount of all monomers (i) and (ii). Polymerization regulators are described in the literature and include, for example, sulfur compounds, sodium hypophosphite, formic acid or tribromochloromethane. Specific examples of sulfur compounds include mercaptoethanol, 2-ethylhexylthioglycolate, thioglycolic acid, and dodecylmercaptan.

The weight average molecular weight of the polymer P Mw is preferably from 75,000 to 5,000,000 Da. The weight average molecular weight of the polymer P Mw is more preferably 100,000 to 4,500,000 Da, most preferably 180,000 to 2,500,000 Da, and even more preferably 210,000 to 1,500,000 Da. The weight average molecular weight can be determined by static light scattering, for example, at pH 9.0 in 1000 mM saline solution.

Polymer P preferably has a cation equivalent of less than 3 meq/g, very preferably less than 2.4 meq/g, more preferably less than 2.2 meq/g and more than 0.1 meq/g, and most preferably from 2.0 meq/g to 0.5 meq/g. The cationic equivalent is preferably determined by titrating an aqueous solution of polymer R, which is adjusted to pH 3 using an aqueous solution of potassium polyvinyl sulfate. The cationic equivalent is more preferably determined by i) providing a predetermined volume of an aqueous solution of polymer P adjusted to pH 3 in a zeta-sizer, e.g. a Mtitek PCD-02 zeta-sizer, ii) titrating the aqueous solution with an aqueous solution of potassium polyvinyl sulfate, e.g. , with a concentration of N/400, to the zero point of the flow potential, and iii) calculation of the electrical charge.

Examples of monomers (i) of formula I include N-vinylformamide (R ¹ is H), N-vinylacetamide (R 1 is C ₁ -alkyl), N-vinylpropionamide (R ¹ is C ₂ -alkyl) and N-vinylbutyramide (R ¹ is C ₃ -alkyl). C ₃ -C ₆ alkyls can be linear or branched. Examples of C ₁ -C ₆ -alkyl include methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 2-methylpropyl, 3-methylpropyl, 1,1-dimethylethyl, n-pentyl, 2-methylbutyl, 3-methylbutyl , 2,2-dimethylpropyl or n-hexyl. R ¹ is preferably H or C ₁ -C ₄ -alkyl, highly preferably H or C ₁ -C ₂ -alkyl, particularly preferably H or C ₁ -alkyl and most preferably H, i.e. the monomer is (i) N-vinylformamide. In addition to the individual monomer of formula I, monomer (i) also includes a mixture of different monomers of formula I. The proportion of monomers wherein R1 is H in the total amount of all monomers (i) of formula I is preferably from 85 to 100%, highly preferably from 90% to 100%, particularly preferably 95 to 100% and most preferably 99 to 100%.

The total amount of all monomers (i) is preferably from 45 to 85 mol.% based on all monomers used in the polymerization to obtain polymer P, i.e. all monomers (i) and (ii) or according to the following designations (ii) sequentially (i), (ii-A), (ii-B), (ii-C) and (ii-D) or (i), ( ii-1), (ii-2), (ii-3), (ii-4), (ii-5), (ii-6), (ii-7) and (ii-8), to a large extent preferably at a concentration of 50 to 83 mol%, particularly preferably at a concentration of 55 to 82 mol%, extremely preferably at a concentration of 60 to 81 mol% and most preferably at a concentration of 62 to 80 mol%.

An ethylenically unsaturated monomer in this context is a monomer containing at least one C ₂ unit, two carbon atoms of which are connected to each other by a carbon-carbon double bond. If the only substituent is a hydrogen atom, then the monomer is ethylene. When three hydrogen atoms are substituted, a vinyl derivative is present. When two hydrogen atoms are substituted, a derivative of the E/Z or ethene-1,1-diyl isomer is present. Monoethylenically unsaturated monomer in this context means that only one C ₂ unit is present in the monomer.

The total amount of all monomers (i) is preferably from 15 to 55 mol.% based on all monomers used in the polymerization to obtain polymer P, i.e. all monomers (i) and (ii) or according to the following designations (ii) sequentially (i), (ii-A), (ii-B), (ii-C) and (ii-D) or (i), ( ii-1), (ii-2), (ii-3), (ii-4), (ii-5), (ii-6), (ii-7) and (ii-8), to a large extent preferably at a concentration of 17 to 50 mol%, particularly preferably at a concentration of 18 to 45 mol%, extremely preferably at a concentration of 19 to 40 mol% and most preferably at a concentration of 20 to 38 mol%.

When polymerizing monomers of formula I, polymer P initially contains amide groups from said monomers. In the case of N-vinylformamide, i.e. formula I, in which R ¹ is H, this group is a formamide group -NH-C(=O)H. As described, for example, in European patent No. EP No. 0438744 A1, page 8 / lines 26-34, the amide group can be hydrolyzed under acidic or alkaline conditions to remove the carboxylic acid and form a primary amino group in the polymer P. Alkaline hydrolysis of the amide group is preferred . If not all amide groups are hydrolyzed, then a cyclic six-membered amidine can be formed by condensation of the primary amino group with an adjacent amide group. In this case, hydrolysis of the amide group leads to the formation of a primary amino group or amidine group in polymer P according to the reaction scheme below.

When polymerizing ethylene derivatives directly substituted in the ethylene functional group by a cyano group, for example, acrylonitrile, polymer P additionally contains cyano groups. It is known that the primary amino group in polymer P, formed during hydrolysis, reacts with one of these cyano groups to form a cyclic five-membered amidine. In this case, hydrolysis of the amide group leads to the formation of an amidine group in polymer P according to the reaction scheme below. In the reaction scheme below, the ethylene derivative substituted with a cyano group is the polymerizable acrylonitrile.

In both cases presented, hydrolysis of the amide group in the monomer of formula I leads to the formation of a primary amino group or amidine group. The primary amino group or amidine group is positively charged at pH 7 and corresponds to the cationic charge of the polymer P.

The conditions for hydrolysis of amide groups in Polymer P derived from monomers of Formula I can also lead to hydrolysis of other groups in Polymer P that are sensitive to hydrolysis under such conditions. As described, for example, in European patent No. EP 0216387 A2, column 6 / lines 7-43, or in application WO 2016/001016 A1, page 17 / lines 1-8, the hydrolysis of acetate groups in the polymer P derived from vinyl acetate , used as monomer (ii). Accordingly, a secondary hydroxyl group is formed in polymer P, as shown below.

Examples of one or more ethylenically unsaturated monomers (ii) include an anionic monomer (ii-A), an uncharged monomer (ii-B), a cationic monomer (ii-C) and a zwitterionic monomer (ii-D). An anionic monomer contains at least one negative charge at pH 7, an uncharged monomer contains no charges at pH 7, a cationic monomer contains at least one positive charge at pH 7, and a zwitterionic monomer contains at least one anionic charge at pH 7 and at least at least one cationic charge. The question of whether an atom or functional group bears a charge at pH 7 can be approximated by considering the behavior of the atom or functional group in a comparable molecular environment of a non-monomer. The anionic monomer (ii-A) is preferably acrylic acid, methacrylic acid or an alkali metal, alkaline earth metal or ammonium salt thereof. The uncharged monomer (ii-B) is acrylonitrile, methacrylonitrile or vinyl acetate.

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-A) anionic monomer,

(ii-B) uncharged monomer,

(ii-C) cationic monomer,

(ii-D) 0-10 mol.% zwitterionic monomer,

where the total amount of all monomers (i) and (ii-A) - (ii-D) is 100 mol.% based on the total amount of all monomers (i) and (ii-A) - (ii-D).

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-A) anionic monomer,

(ii-B) uncharged monomer,

(ii-C) cationic monomer,

(ii-D) 0-10 mol.% zwitterionic monomer,

wherein at least one ethylenically unsaturated monomer is an anionic monomer or an uncharged monomer,

where the total amount of all monomers (i) and (ii-A) - (ii-D) is 100 mol.% based on the total amount of all monomers (i) and (ii-A) - (ii-D).

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-A) an anionic monomer, wherein at least 50% of all anionic monomers are acrylic acid, methacrylic acid or their alkali metal, alkaline earth metal or ammonium salts based on the total number of anionic monomers,

(ii-B) an uncharged monomer, wherein at least 50% of all uncharged monomers are vinyl acetate, acrylonitrile or methacrylonitrile based on the total number of all uncharged monomers,

(ii-C) cationic monomer,

(ii-D) 0-10 mol.% zwitterionic monomer,

wherein at least one ethylenically unsaturated monomer is an anionic monomer or an uncharged monomer,

where the total amount of all monomers (i) and (ii-A) - (ii-D) is 100 mol.% based on the total amount of all monomers (i) and (ii-A) - (ii-D).

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-A) an anionic monomer, wherein at least 50% of all anionic monomers are acrylic acid, methacrylic acid or their alkali metal, alkaline earth metal or ammonium salts based on the total number of anionic monomers,

(ii-B) an uncharged monomer, wherein at least 50% of all uncharged monomers are vinyl acetate, acrylonitrile or methacrylonitrile based on the total number of all uncharged monomers,

(ii-C) 0-15 mol.% cationic monomer,

(ii-D) 0-10 mol.% zwitterionic monomer,

where at least one ethylenically unsaturated monomer is an anionic monomer or an uncharged monomer, and the amount of anionic monomers and uncharged monomers is from 15 to 60 mol.%,

where the total amount of all monomers (i) and (ii-A) - (ii-D) is 100 mol.% based on the total amount of all monomers (i) and (ii-A) - (ii-D).

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-A) an anionic monomer, wherein at least 50% of all anionic monomers are acrylic acid, methacrylic acid or their alkali metal, alkaline earth metal or ammonium salts based on the total number of anionic monomers,

(ii-B) an uncharged monomer, wherein at least 50% of all uncharged monomers are vinyl acetate, acrylonitrile or methacrylonitrile based on the total number of all uncharged monomers,

where the total amount of all monomers (i) and (ii-A) - (ii-B) is 100 mol.% based on the total amount of all monomers (i) and (ii-A) - (ii-B).

One or more ethylenically unsaturated monomers (ii) are preferably selected from

(ii-1) acrylic acid or methacrylic acid or their alkali metal, alkaline earth metal or ammonium salts,

(ii-2) acrylonitrile or methacrylonitrile,

(ii-3) vinyl acetate,

(ii-4) a monoethylenically unsaturated sulfonic acid, a monoethylenically unsaturated phosphonic acid, a monoethylenically unsaturated phosphoric acid ester or a monoethylenically unsaturated carboxylic acid containing from 4 to 8 carbon atoms, which is different from methacrylic acid, or their alkali metal, alkaline earth metal or ammonium salts,

(ii-5) a quaternized monoethylenically unsaturated monomer, a monoethylenically unsaturated monomer containing at least one secondary or tertiary amino group and in which at least one secondary or tertiary amino group is protonated at pH 7, or a diallyl-substituted amine that contains only two ethylene double bonds and is quaternized or protonated at pH 7, or their salt forms,

(ii-6) a monoethylenically unsaturated monomer which does not contain a charge at pH 7 and which is different from acrylonitrile, methacrylonitrile and vinyl acetate, or an ethylenically unsaturated monomer whose only two ethylenic double bonds are conjugated and which does not contain a charge at pH 7,

(ii-7) from 0 to 2 mol.% of a monomer containing at least two ethylenically unsaturated double bonds that are not conjugated, and which is different from a diallyl-substituted amine, which contains only two ethylenic double bonds,

(ii-8) from 0 to 10 mol.% ethylenically unsaturated monomer, which is different from monomers (i) and from (ii-1) to (ii-7),

where the total amount of all monomers (i) and (ii-1) - (ii-8) is 100 mol.% based on the total amount of all monomers (i) and (ii-1) - (ii-8).

Monomers (ii-1) and (ii-4) are examples of anionic monomer (ii-A). Monomers (ii-2), (ii-3) and (ii-6) are examples of uncharged monomer (ii-B). Monomers (ii-5) are examples of cationic monomer (ii-C). Monomer (ii-8) may be an example of a zwitterionic monomer (ii-D).

Alkali metal, alkaline earth metal or ammonium salts contain, for example, sodium ions, potassium ions, magnesium ions, calcium ions or ammonium ions as cations. Accordingly, alkali or alkaline earth metal bases, ammonia, amines or alkanolamines have been used to neutralize the free acids. For example, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate, potassium carbonate, sodium bicarbonate, manganese oxide, calcium hydroxide, calcium oxide, triethanolamine, ethanolamine, morpholine, diethylenetriamine or tetraethylenepentamine were used. Preferred are alkali metal and ammonium salts, most preferred are sodium, potassium or ammonium (NH4) ⁺ salts.

The list of monomers (ii-4) does not include monomers with a group that is simultaneously protonated at pH 7, or containing a quaternary nitrogen atom.

In the case of monomers (ii-4), the monoethylenically unsaturated sulfonic acids are, for example, vinyl sulfonic acid, acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, metallyl sulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxyrylsulfonic acid a or styrene sulfonic acid .

In the case of monomers (ii-4), the monoethylenically unsaturated phosphonic acids are, for example, vinylphosphonic acid, vinylphosphonic acid monomethylester, allylphosphonic acid, allylphosphonic acid monomethylester, acrylamidomethylpropylphosphonic acid or acrylamidomethylenephosphonic acid.

In the case of monomers (ii-4), the monoethylenically unsaturated mono- and diesters of phosphoric acid are, for example, monoallylphosphoric acid esters, methacrylethylene glycol phosphoric acid or methacrylethylene glycol phosphoric acid.

Monomers (ii-4) are monoethylenically unsaturated carboxylic acids containing from 4 to 8 carbon atoms and different from methacrylic acid, for example, dimethacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid or crotonic acid.

The list of monomers (ii-5) does not include a monomer that simultaneously contains a group that deprotonates at pH 7. In the case of monomer (ii-5), the salt form means that the corresponding anion provides charge neutralization in the case of quaternization of the nitrogen atom or in the case of protonation. Such anions are, for example, chloride, bromide, hydrogen sulfate, sulfate, hydrogen phosphate, methyl sulfate, acetate or formate. Chloride and hydrogen sulfate are preferred, and chloride is particularly preferred.

For monomers (ii-5), quaternized monoethylenically unsaturated monomers are, for example, [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [3-(acryloyloxy)propyl]trimethylammonium chloride, [3- (methacryloyloxy)propyl]trimethylammonium chloride, 3-(acrylamidopropyl)trimethylammonium chloride or 3-(methacrylamidopropyl)trimethylammonium chloride. Preferred quaternizing agents used are dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride or benzyl chloride. Most preferred is methyl chloride.

For monomers (ii-5), monoethylenically unsaturated monomers containing at least one secondary or tertiary amino group that is protonated at pH 7 were used, for example, esters of α, β-ethylenically unsaturated monocarboxylic acids and amino alcohols, α mono- and diesters, β-ethylenically unsaturated dicarboxylic acids and amino alcohols, amides of α, β-ethylenically unsaturated monocarboxylic acids and dialkylated diamines, vinylimidazole or alkylvinylimidazole.

In esters of α, β-ethylenically unsaturated monocarboxylic acids and amino alcohols, the acid component is preferably acrylic acid or methacrylic acid. Amino alcohols, preferably C ₂ -C ₁₂ amino alcohols, can be C ₁ -C ₈ mono- or C ₁ -C ₈ dialkylated amino alcohols at the amine nitrogen atom. Examples include dialkylaminoethyl acrylates, dialkylaminoethyl methacrylates, dialkylaminopropyl acrylates, or dialkylaminopropyl methacrylates. Specific examples include N-methylaminoethyl acrylate, N-methylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminopropylacrylate, N, N-dimethacrylate-diethylaminopropylacrylate, N , N-diethylaminopropyl methacrylate, N, N-diethylaminocyclohexyl acrylate or N, N-diethylaminocyclohexyl methacrylate.

In mono- and diesters of α, β-ethylenically unsaturated dicarboxylic acids and amino alcohols, the acid component is preferably fumaric acid, maleic acid, monobutyl maleate, itaconic acid and crotonic acid. Amino alcohols, preferably C ₂ -C ₁₂ amino alcohols, can be C ₁ -C ₈ -mono- or C ₁ -C ₈ -dialkylated amino alcohols at the amine nitrogen atom.

Amides of α, β-ethylenically unsaturated monocarboxylic acids and dialkylated diamines are, for example, dialkylaminoethyl acrylamides, dialkylaminoethyl methacrylamides, dialkylaminopropylacrylamides or dialkylaminopropylacrylamides. Specific examples include N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(dimethylamino)ethyl]methacrylamide, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide , N-[4-(dimethylamino)butyl]acrylamide, N-[4-(dimethylamino)butyl]methacrylamide, N-[2-(diethylamino)ethyl]acrylamide or N-[2-(diethylamino)ethyl]methacrylamide.

Diallyl-substituted amines containing only two ethylene double bonds, quaternized or protonated at pH 7, such as diallylamine or diallyldimethylammonium chloride, were used as monomers (ii-5).

Examples of monomers (ii-6) include monoesters of α, β-ethylenically unsaturated monocarboxylic acids and C ₁ -C ₃₀ alkanols, monoesters of α, β-ethylenically unsaturated monocarboxylic acids and C ₂ -C ₃₀ alkanediols, diesters of α, β-ethylenically unsaturated dicarboxylic acids and C ₁ -C ₃₀ alkanols or C ₂ -C ₃₀ alkanediols, primary amides of α, β-ethylenically unsaturated monocarboxylic acids, N-alkylamides of α, β-ethylenically unsaturated monocarboxylic acids, N, N-dialkylamides of α, β-ethylenically unsaturated monocarboxylic acids, α nitriles, β-ethylenically unsaturated monocarboxylic acids other than acrylonitrile and methacrylonitrile, dinitriles of α, β-ethylenically unsaturated dicarboxylic acids, esters of vinyl alcohol and C ₁ - or C ₃ -C ₃₀ -monocarboxylic acids, esters of allyl alcohol and C ₁ -C ₃₀ - monocarboxylic acids, N-vinyl lactams, nitrogen-free heterocycles with α, β-ethylenically unsaturated double bonds, vinyl aromatic compounds, vinyl halides, vinylidene halides, C ₂ -C ₈ monoolefins or C ₄ -C ₁₀ olefins containing only two double bonds that are conjugated.

Monoesters are, for example, methyl acrylate, methyl methacrylate, methyl ethacrylate (= methyl-2-ethyl acrylate), ethyl acrylate, ethyl methacrylate, ethyl ethacrylate (= ethyl-2-ethyl acrylate), n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert -butyl methacrylate, tert-butyl ethacrylate, n-octyl acrylate, n-octyl methacrylate, 1,1,3,3-tetramethylbutyl acrylate, 1,1,3,3-tetramethylbutyl methacrylate or 2-ethylhexyl acrylate.

Monoeses of α, β-ethylene-saturated monocarbon acids and C2-C30-Alkandiols are, for example, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrilate, 2-hydroxyethylEtacrylate, 2-hydroxiproalite, 2-hydroxypropylmetakrilate, 3-gi-gi-gi-gydroxiproxylate, 3 -ydroxypropilmetacrylate, 3-hydroxybulacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl acrylate or 6-hydroxyhexyl methacrylate.

Primary amides of α, β-ethylenically unsaturated monocarboxylic acids include, for example, acrylic acid amide or methacrylic acid amide.

N-alkylamides of α, β-ethylenically unsaturated monocarboxylic acids are, for example, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-(n-propyl)acrylamide, N-( n-propyl)methacrylamide, N-(n-butylacrylamide, N-(n-butyl)methacrylamide, N-(tert-butyl)acrylamide, N-(tert-butyl)methacrylamide, N-(n-octyl)acrylamide, N -(n-octyl)methacrylamide, N-(1,1,3,3-tetramethylbutyl)acrylamide, N-(1,1,3,3-tetramethylbutyl)methacrylamide, N-(2-ethylhexyl)acrylamide or N-( 2-ethylhexylmethacrylamide).

Examples of N,N-dialkylamides of α,β-ethylenically unsaturated monocarboxylic acids include N,N-dimethylacrylamide or N,N-dimethylmethacrylamide.

Esters of vinyl alcohol and C1 or C3-C30 monocarboxylic acids are, for example, vinyl formate or vinyl propionate.

Examples of N-vinyl lactams include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2 -piperidone, N-vinyl-6-ethyl-2-piperidone, N-vinyl-7-methyl-2-caprolactam or N-vinyl-7-ethyl-2-caprolactam.

Examples of vinyl aromatic compounds are styrene or methylstyrene.

Vinyl halides are, for example, vinyl chloride or vinyl fluoride.

Vinylidene halides are, for example, vinylidene chloride or vinylidene fluoride.

C ₂ -C ₈ -monoolefins are, for example, ethylene, propylene, isobutylene, 1-butene, 1-hexene or 1-octene.

₄ -C ₁₀ -olefins with only two double bonds that are conjugated are, for example, butadiene or isoprene.

Monomers (ii-7) act as crosslinkers. Examples of monomers (ii-7) include triallylamine, methylene bisacrylamide, diacrylate glycol, dimethacrylate glycol, glycerol triacrylate, pentaerythritol triallyl ether, N,N-divinylethylene urea, tetraallylammonium chloride, polyalkylene glycol sorbate or at least doubly esterified with acrylic acid and/or methacrylic acid or methacryls oh an acid such as pentaalkylene glycol.

Examples of monomers (ii-8) include sulfobetaine 3-(dimethyl(methacryloylethyl)ammonium)propanesulfonate, sulfobetaine 3-(2-methyl-5-vinylpyridinium)propanesulfonate, carboxybetaine N-3-methacrylamidopropyl-N,N-dimethyl-β-ammonium propionate, carboxybetaine N-2-acrylamidoethyl-N,N-dimethyl-β-ammonium propionate, 3-vinylimidazole-N-oxide, 2-vinylpyridine-N-oxide or 4-vinylpyridine-N-oxide.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

(ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali metal, alkaline earth metal or ammonium salts,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-1) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A largely preferred amount is (i) 50 to 83 mol%, (ii) 17 to 50 mol%, and (ii-1) 17 to 50 mol%. Particularly preferred is the amount of (i) 55 to 82 mol%, (ii) 18 to 45 mol% and (ii-1) 18 to 45 mol%. Particularly preferred is the amount of (i) 60 to 81 mol%, (ii) 19 to 40 mol% and (ii-1) 19 to 40 mol%. Most preferred is the amount of (i) 62 to 80 mol%, (ii) 20 to 38 mol% and (ii-1) 20 to 38 mol%.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-2) contains from 0 to 35 mol.% acrylonitrile or methacrylonitrile,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-2) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. Depending on the chosen hydrolysis conditions of polymer P, the cyano and nitrile groups of the polymerizing monomers (ii-2) can also be partially hydrolyzed to a carboxamide group or a carboxyl group. In the case of hydrolysis, the cyano group or nitrile group can also react with the polymerizing monomer (i) to form a cyclic 5-membered amidine. A content of monomers (ii-2) of 0 to 34 mol% is highly preferred, 0.1 to 34 mol% is particularly preferred and 1 to 27 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

(ii-3) 0 to 35 mol% vinyl acetate is present,

and optionally with subsequent partial or complete hydrolysis of groups of monomers (i) polymerizing into polymer P.

The content of monomers (ii-3) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. In the case of hydrolysis, the acetate groups of the copolymerizing monomers (ii-3) can also be partially or completely hydrolyzed to secondary hydroxyl groups. A content of monomers (ii-3) of 0 to 34 mol% is highly preferred, 0.1 to 34 mol% is particularly preferred and 1 to 27 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-4) contains from 0 to 10 mol.% of a monoethylenically unsaturated sulfonic acid, a monoethylenically unsaturated phosphonic acid, a monoethylenically unsaturated phosphoric acid mono- or di-ester or a monoethylenically unsaturated carboxylic acid containing from 4 to 8 carbon atoms other than methacrylic acid, or their alkali or alkaline earth metal or ammonium salts,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-4) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A content of monomers (ii-4) of 0 to 5 mol% is highly preferred, 0.1 to 5 mol% is particularly preferred and 1 to 3 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-5) contains from 0 to 20 mol.% quaternized monoethylenically unsaturated monomer containing at least one secondary or tertiary amino group that is protonated at pH 7, or diallyl-substituted amine containing only two ethylenic double bonds, which is quaternized or which protonated at pH 7, or its salt form,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-5) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A content of monomers (ii-5) of 0 to 34 mol% is highly preferred, 0.1 to 34 mol% is particularly preferred and 1 to 27 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-6) contains from 0 to 35 mol.% monoethylenically unsaturated monomer, which does not contain a charge at pH 7 and is different from acrylonitrile, methacrylonitrile and vinyl acetate, or an ethylenically unsaturated monomer, only two of whose ethylenic double bonds are conjugated and do not carry a charge at pH 7 and which is different from acrylonitrile, methacrylonitrile and vinyl acetate,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-6) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A content of monomers (ii-6) of 0 to 34 mol% is highly preferred, 0.1 to 34 mol% is particularly preferred and 1 to 27 mol% is extremely preferred.

Preferred is polymer P, which is produced by polymerization using less than 5 mol% acrylamides as monomer (ii), more preferably less than 1 mol% acrylamide, and most preferably no acrylamide.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-7) contains from 0 to 1 mol.% of a monomer containing at least two ethylenically unsaturated double bonds that are not conjugated, and which is different from a diallyl-substituted amine, which contains only two ethylenic double bonds,

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-7) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A content of monomers (ii-7) of 0 to 0.5 mol% is highly preferred, 0.001 to 0.5 mol% is particularly preferred, and 0.01 to 0.1 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii) from 15 to 50 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where among monomers (ii)

monomer (ii-8) contains from 0 to 5 mol.% ethylenically unsaturated monomers different from monomers (i) and (ii-1) - (ii-7)

and optionally with subsequent partial or complete hydrolysis of the monomer units (i) polymerizing into polymer P.

The content of monomers (ii-7) in molar percentage corresponds to the total number of all monomers (i) and (ii), i.e. all monomers used in polymerization. The total amount of all monomers is 100 mol.%. A content of monomers (ii-8) of 0 to 3 mol% is highly preferred, 0.1 to 3 mol% is particularly preferred, and 1 to 2 mol% is extremely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali, alkaline earth or ammonium salts,

(ii-2) from 0 to 35 mol.% acrylonitrile or methacrylonitrile,

(ii-3) from 0 to 35 mol.% vinyl acetate,

(ii-4) from 0 to 35 mol.% monoethylenically unsaturated sulfonic acid, monoethylenically unsaturated phosphonic acid, monoethylenically unsaturated phosphoric acid mono- or diester or monoethylenically unsaturated carboxylic acid containing from 4 to 8 carbon atoms, which is different from methacrylic acid, or alkaline thereof , alkaline earth or ammonium salts.

(ii-5) from 0 to 35 mol.% quaternized monoethylenically unsaturated monomer that contains at least one secondary or tertiary amino group that is protonated at pH 7, or diallyl-substituted amine that contains only two ethylenic double bonds and is quaternized or protonated at pH 7, or their salt form,

(ii-6) from 0 to 35 mol.% of a monoethylenically unsaturated monomer containing no charge at pH 7 and other than acrylonitrile, methacrylonitrile and vinyl acetate, or an ethylenically unsaturated monomer of which only two ethylenically unsaturated double bonds are conjugated and uncharged at pH 7,

(ii-7) from 0 to 2 mol.% of a monomer containing at least two ethylenically unsaturated double bonds that are not conjugated and that are different from a diallyl-substituted amine that contains only two ethylenic double bonds,

(ii-8) from 0 to 10 mol.% ethylenically unsaturated monomer, different from monomers (i) and (ii-1) - (ii-7),

and optionally by subsequent partial hydrolysis of the monomer units of formula (I) which polymerize into polymer P to form amino groups or amidine groups, the ester group being partially or completely hydrolyzed by the polymerizing vinyl acetate, the total amount of all monomers (i) and (ii-1 ) - (ii-8) is 100 mol.% based on the total amount of all monomers (i) and (ii-1) - (ii-8). A content of monomer (i) in an amount of 50 to 83 mol% and monomer (ii-1) in an amount of 17 to 50 mol% is largely preferred. A content of monomer (i) in an amount of 55 to 82 mol% and monomer (ii-1) in an amount of 18 to 45 mol% is particularly preferred. A content of monomer (i) of 60 to 81 mol% and monomer (ii-1) of 19 to 40 mol% is highly preferred. A content of monomer (i) in an amount of 62 to 80 mol% and monomer (ii-1) in an amount of 20 to 38 mol% is largely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali, alkaline earth or ammonium salts,

(ii-2) from 0 to 35 mol.% acrylonitrile or methacrylonitrile,

(ii-3) from 0 to 35 mol.% vinyl acetate,

and optionally by subsequent partial or complete hydrolysis of the monomer units of formula (I) which polymerize into polymer P to form amino groups or amidine groups, the ester group being partially or completely hydrolyzed by the polymerizing vinyl acetate, the total amount of all monomers (i), (ii -1), (ii-2) and (ii-3) is 100 mol.% and the mole percentages refer to the total amount of all monomers (i), (ii-1), (ii-2) and (ii-3) . A content of monomer (i) in an amount of 50 to 83 mol% and monomer (ii-1) in an amount of 17 to 50 mol% is largely preferred. A content of monomer (i) in an amount of 55 to 82 mol% and monomer (ii-1) in an amount of 18 to 45 mol% is particularly preferred. A content of monomer (i) of 60 to 81 mol% and monomer (ii-1) of 19 to 40 mol% is highly preferred. A content of monomer (i) in an amount of 62 to 80 mol% and monomer (ii-1) in an amount of 20 to 38 mol% is largely preferred.

Preferred is polymer P, which is obtained by polymerization

(i) from 50 to 85 mol.% of the monomer of formula I,

(ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali, alkaline earth or ammonium salts,

(ii-2) from 0 to 35 mol.% acrylonitrile or methacrylonitrile,

and optionally upon subsequent partial or complete hydrolysis of the monomer units of formula (I) which polymerize into polymer P to form amino groups or amidine groups, the total amount of all monomers (i), (ii-1) and (ii-2) is 100 mol. % and mole percentages refer to the total amount of all monomers (i), (ii-1) and (ii-2). A content of monomer (i) in an amount of 50 to 83 mol% and monomer (ii-1) in an amount of 17 to 50 mol% is largely preferred. A content of monomer (i) in an amount of 55 to 82 mol% and monomer (ii-1) in an amount of 18 to 45 mol% is particularly preferred. A content of monomer (i) of 60 to 81 mol% and monomer (ii-1) of 19 to 40 mol% is highly preferred. A content of monomer (i) in an amount of 62 to 80 mol% and monomer (ii-1) in an amount of 20 to 38 mol% is largely preferred.

The method is preferably carried out in a paper machine. The paper machine is preferably provided with equipment that includes a first wire section with a first screen that includes an upper side of the first screen and a bottom side of the first screen, and a second screen section with a second screen that includes an upper side of the second screen and a bottom side of the second screen, a spray device, containing a spray solution or a spray suspension, a pressing section and a drying section with heated cylinders, and this equipment is arranged in the paper machine in the following order: a first wire part and a second wire part, followed by a spray device, then a pressing section and a drying section. The spray device is preferably located at the end of the first mesh section and the second mesh section. In a paper machine, step (A) is carried out in the first wire section, step (B) in the second wire section, step (C) before the pressing section, preferably at the end of the first wire section and the second wire section, step (D) is carried out before or at the beginning pressing sections, step (E) is carried out in the pressing section and step (F) is carried out in the drying section. The spray device preferably includes at least one or more spray nozzles, very preferably one or more spray nozzles, which enable the spray solution or suspension to be sprayed at an increased pressure of 0.5 to 4.5 bar compared to ambient pressure. The first fiber slurry and the second fiber slurry are passed through a papermaking machine, including dehydration on the meshes, spraying on at least one side of the surface and joining the webs, dehydration by pressing and applying heat to the multi-layer paper in the direction from the mesh sections to the drying section.

The advantages of the method for producing multi-layer paper can be applied to other objects of the present invention.

Another object of the present invention is dried multi-layer paper, which is obtained by a process comprising the following steps

(A) Dehydrating the first aqueous fibrous suspension, in which the solids content is from 0.1 wt.% to 6 wt.%, on the first grid, thereby forming a first fibrous web, in which the solids content is from 14 wt.% up to 25 wt.%,

(B) Dehydrating a second fibrous suspension in which the solids content is from 0.1 wt.% to 6 wt.% on the second grate, thereby forming a second fibrous web in which the solids content is from 14 wt.% to 25 wt.%,

(C) Spraying a spray solution or spray suspension onto at least one side of the surface of the first fibrous web, the second fibrous web, or the first fibrous web and the second fibrous web, thereby obtaining at least one surface-side sprayed fibrous web,

(D) Connecting a first fibrous web to a second fibrous web, and at least one of the two is a sputtered fibrous web, such that at least one side of the sputtered surface of the two fibrous webs forms a contact side of the surface with the other fibrous web, and so that the fibrous webs were arranged one above the other across the entire width, thus forming a layered material,

(E) Dehydration of the laminate by pressing, thereby producing a partially dehydrated laminate,

(F) Dehydrating the partially dehydrated laminate by applying heat to form a dried laminate paper,

wherein the solution to be sprayed or the suspension to be sprayed contains

(s-a) water

(c-b) at least one water-soluble polymer P, which can be obtained by polymerization

from 40 to 85 mol.% monomer of formula I

where R ¹ means H or C ₁ -C ₆ -alkyl,

(ii) from 15 to 60 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where the total amount of monomers (i) and (ii) is 100 mol.%,

and optionally by subsequent partial or complete hydrolysis of the monomer units of formula (I), which are polymerized to obtain polymer P, in which primary amino groups and amidine groups are formed,

where the proportion of water is at least 75 wt.% based on the sprayed solution or sprayed suspension.

The dried multi-layer paper is preferably produced by a process in which the pH of the spray solution or spray suspension is 5.5 or more.

The dry matter content is preferably determined by drying at 105°C to constant weight.

The solids content of the dry multi-ply paper is preferably at least 88% by weight.

Dry multi-layer paper preferably consists of two layers, very preferably one layer with a weight of 20 to 60 g/m ² and another with a weight of 60 to 100 g/m ² .

The internal bond strength of the dry multi-ply paper is preferably 200 to 450 J/m ² , more preferably 210 to 400 J/m ² and most preferably 230 to 380 J/m ² where the internal bond strength is in accordance with the rules of the Pulp Technical Association paper industry (Tappi) T833 pm-94.

Another object of the present invention is a paper machine, the equipment of which includes a first mesh section with a first mesh that contains an upper side of the first mesh and a lower side of the first mesh, and a second mesh section with a second mesh that contains an upper side of the second mesh and a lower side of the second mesh, a spray device containing a spray solution or spray suspension, a pressing section and a drying section with heated cylinders, and this equipment is arranged in the paper machine in the following order: a first wire part and a second wire part, followed by a spray device, then a pressing section and a drying section , wherein the spray device contains a sprayable solution or a sprayable suspension.

wherein the solution to be sprayed or the suspension to be sprayed contains

(s-a) water

(c-b) at least one water-soluble polymer P, which can be obtained by polymerization

from 40 to 85 mol.% monomer of formula I

where R ¹ means H or C ₁ -C ₆ -alkyl,

(ii) from 15 to 60 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I,

where the total amount of monomers (i) and (ii) is 100 mol.%,

and optionally by subsequent partial or complete hydrolysis of the monomer units of formula (I), which are polymerized to obtain polymer P, in which primary amino groups and amidine groups are formed,

where the proportion of water is at least 75 wt.% based on the sprayed solution or sprayed suspension,

and the paper machine is suitable for a process for producing dry multi-ply paper comprising the following steps

(A) Dehydrating the first aqueous fibrous suspension, in which the dry matter content is from 0.1 wt.% to 6 wt.%, on the first grate, thereby forming a first fibrous web, in which the dry matter content is in an amount of from 14 wt. % up to 25 wt.%,

(B) Dehydrating a second fibrous suspension in which the solids content is from 0.1 wt.% to 6 wt.% on the second grid, thereby forming a second fibrous web in which the solids content is from 14 wt.% to 25 wt.%,

(C) Spraying the spray solution or spray suspension onto at least one side of the surface of the first fibrous web, the second fibrous web, or the first fibrous web and the second fibrous web, thereby obtaining one fibrous web sprayed on the surface side,

(D) Connecting a first fibrous web to a second fibrous web, and at least one of the two is a sputtered fibrous web, such that at least one side of the sputtered surface of the two fibrous webs forms a contact side of the surface with the other fibrous web, and so that the fibrous webs were arranged one above the other across the entire width, thus forming a layered material,

(E) Dehydration of the laminate by pressing, thereby producing a partially dehydrated laminate,

(F) Dehydration of the partially dehydrated laminate by applying heat to form a dried laminate paper.

The pH value of the sprayed solution or sprayed suspension in the spray device is 5.5 or more.

The dry matter content is preferably determined by drying at 105°C to constant weight.

Preferred is a paper machine comprising a device for generating negative pressure on the underside of the first mesh or on the underside of the second mesh. More preferably, a papermaking machine includes a device for generating negative pressure on the underside of the first mesh and a device for generating negative pressure on the underside of the second mesh.

Preferably, a paper machine has a first wire section and a second wire section arranged such that the first fiber fiber and the second fiber fiber are sprayed simultaneously from a single spray device, wherein the spraying occurs between the end of the two wire sections and the beginning of the pressing section, and when two sides of the sprayed surface of the first fibrous web and the second fibrous web are in contact with each other when they are connected.

Another invention is a method for producing dry multi-layer paper, in which polymer P is replaced by polymer PA compared to the previous method. The objects of such another invention, in addition to the above-mentioned method, are also the corresponding paper obtained by this method and a paper machine suitable for this method, which contains a spray device containing an aqueous spray solution or spray suspension with polymer PA. Polymer PA, which is different from polymer P, is a Michael-modified polymer P containing primary amine groups, an alkylated polyvinylamine containing primary amine groups, or a graft polymer containing primary amine groups.

A modified Michael system polymer containing primary amine groups can be obtained by providing Michael systems with a parent polymer containing primary amine groups. This application of a type of polymer characterized by structural formula II:

described in WO 2007/136756.

The Michael system should be understood as compounds containing an unsaturated double bond conjugated to an electron-withdrawing group. Suitable Michael systems are characterized by formula III.

where R ² and R ³ are independently H, alkyl, alkenyl, carbonyl, carboxyl or carboxamide, and X ¹ is an electron-withdrawing group or an electron-withdrawing amine.

Typical Michael systems include acrylamide, N-alkylacrylamide, methacrylamide, N,N-dimethylacrylamide, N-alkylmethacrylamide, N-(2-methylpropanesulfonic acid) acrylamide, N-(glycolic acid) acrylamide, N-[3-(propyl)trimethylammonium chloride acrylamide ], acryloniril, methacrylonitrile, acrolein, methyl acrylate, alkyl acrylate, methyl methacrylate, alkyl methacrylate, arylacrylate, aryl methacrylate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, N-[3-(dimethylamino)propyl]methacrylamide, N-ethylacrylamide, 2-hydroxyethyl acrylate, 3-sulfopropylacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, pentafluorophenylacrylate, ethylene diacrylate, ethylene dimethacrylate, heptafluorobutyl-1-acrylate, polymethyl methacrylate, acryloylmorpholine, 3-(acryloyloxy)-2-hydroxypropyl methacrylate, dialkylethyl acrylate, dialkyl methyl acrylate, dialkylethyl acrylate, 1-adamantyl methacrylate, dimethylaminoneopentyl acrylate, 2- (4-benzoyl-3-hydroxyphenoxy)ethyl acrylate and dimethylaminoethyl methacrylate.

Michael's preferred system is acrylamide. Michael systems are used in amounts from 1 to 75 mol.% based on primary amino groups and/or amidine groups. The reaction conditions are described in WO 2007/136756, the entire contents of which are incorporated herein by reference.

Alkylated polyvinylamine containing primary amino groups is obtained as a result of reactions of primary amino groups and/or amidine groups in polyvinylamines. The preparation of these compounds, as well as the reaction conditions, are described in application WO 2009/017781. The claimed products preferably contain structural units selected from the group of polymer units characterized by structural formulas (IV), (V), (VI), (VII) and (VIII):

Where

X ^is an anion, preferably a chloride anion, bromide anion or iodide anion,

Y means carbonyl or methylene or single bond,

R ⁴ means hydrogen, linear or branched C ₁ -C ₂₂ alkyl,

R ⁵ means linear or branched C ₁ -C ₁₅ alkylene, or linear or branched C ₁ -C ₁₅ alkenylene,

R ⁶ means linear or branched C ₁ -C ₁₂ alkylene, which is optionally substituted with hydroxyl, preferably means -CH ₂ CH(OH)CH ₂ - or -CH ₂ -CH ₂ -,

R ⁷ means hydrogen, linear or branched C ₁ -C ₂₂ alkyl, preferably methyl or ethyl,

R ⁸ means hydrogen, linear or branched C ₁ -C ₂₂ alkyl, linear or branched C ₁ -C ₂₂ alkoxy, linear or branched C ₁ -C ₂₂ dialkylamino, preferably an amino group,

R ⁹ means linear or branched C ₁ -C ₁₂ alkylene, preferably -CH ₂ -CH ₂ -,

R ¹⁰ means hydrogen, linear or branched C ₁ -C ₂₂ alkyl, preferably methyl or ethyl.

The claimed products, which contain units of formula IV, can be obtained by a polymer-analogous reaction of primary amino groups in polyvinylamines with alkylating agents. Alkylation can also be carried out using alkyl glycidyl ethers, glycidol (2,3-epoxy-1-propanol) or chloropropanediol. Preferred alkyl glycidyl ethers are butyl glycidyl ether, 2-ethylhexyl glycidyl ether, hexadecyl glycidyl ether and C ₁₂ /C ₁₄ glycidyl ether. This reaction involving alkyl glycidyl ethers is usually carried out in water, but it can also be carried out in mixtures of aqueous-organic solvents.

The claimed products containing units of formulas V and VII can be obtained by a polymer analogous reaction of primary amino groups in polyvinylamines with alkylating agents or acylating agents.

Said alkylating agents are selected from chloroacetic acid, chloroacetic acid salts, bromoacetic acid, bromoacetic acid salts, halogenated alkanoic acid acrylamides and halogenated alkenoic acid acrylamides, 3-chloro-2-hydroxypropyltrimethylammonium chloride, 2-(diethylamino)ethylchloroethylamylethylaminoethyl (di methylamino) ethylamine chloride, (dialkyl)-3-chloro-2-hydroxypropyl alkyl dimethyl ammonium chlorides such as 3-chloro-2-hydroxypropyl lauryl dimethyl ammonium chloride, 3-chloro-2-hydroxypropyl cocoalkyl dimethyl ammonium chloride, 3-chloro-2-hydroxypropyl stearyl dimethyl ammonium chloride, (haloalkyl)-trimethyl ammonium chloride such as ( 4)-(6-chlorohexyl)trimethylammonium chloride, (8-chlorooctyl)trimethylammonium chloride, and glycidylpropyltrimethylammonium chloride.

Said acylating agents are selected from succinic anhydride, substituted succinic anhydrides which are substituted with linear or cross-linked C ₁ -C ₁₈ alkyl or linear or cross-linked C ₁ -C ₁₈ alkenyl, maleic anhydride, glutaric anhydride, 3-methylglutaric anhydride, 2,2-dimethylsuccinic anhydride anhydride, cyclic alkenylcarboxylic anhydrides and alkenylsuccinic anhydrides (ASA).

The graft polymer, which contains primary amino groups, includes, for example, hydrolyzable graft polymers, for example, N-vinylformamide-grafted polyalkylene glycols, polyvinyl acetate, polyvinyl alcohol, polyvinylformamides, polysaccharides such as starch, oligosaccharides or monosaccharides. Graft polymers are prepared by radical polymerization of, for example, N-vinylformamide in an aqueous medium in the presence of at least one of said grafting bases, if applicable, along with other copolymerizable monomers, and then hydrolyzing the grafted vinylformamide units in a known manner to produce copolymer units vinylamine. Such graft polymers are described, for example, in the patents DE-A-19515943, DE-A-4127733 and DE-A-10041211.

Examples

The percentages shown in the examples are by weight unless otherwise noted.

A) Addition

A-1) Methods for characterizing polymers

Solids content was determined by spreading 0.5 to 1.5 g of polymer solution onto a 4 cm diameter metal substrate and then drying in a forced air oven at 140°C for 120 min. By dividing the mass of the sample after drying under the above conditions by the mass of the weighed sample and multiplying by 100, the solids content of the polymer solution in wt.% was obtained. Drying was carried out at atmospheric pressure, possibly at 101.32 kPa, without correction for variations due to weather and altitude.

The degree of hydrolysis is the proportion (%) of hydrolyzed N-CHO groups in the N-vinylformamide monomer units used in the polymerization out of the total amount of N-vinylformamide used in the polymerization. The degree of hydrolysis of homopolymers or copolymers polymerized using N-vinylformamide and undergoing hydrolysis was determined by enzymatic analysis of formic acid or formates released during hydrolysis (assay kit from Boehringer Mannheim).

Polymer content means the amount (wt.%) of polymer without counterions in an aqueous solution, that is, the mass of counterions is not taken into account. The polymer content is the sum of the parts by weight (g) of all structural units of the polymer that are present in 100 g of aqueous solution. This value is determined mathematically. For this purpose, structural units that can potentially carry a charge are included in the calculation in a charged form, for example, amino groups are considered in a protonated form, and acid groups in a deprotonated form. The mass of counterions of charged structural units, such as sodium cation, chloride anion, phosphate anion, formate anion, acetate anion, etc., is not taken into account. The calculation can be carried out in such a way that, taking into account the batch, the amount of monomers used, if necessary the degree of hydrolysis of certain monomers and, optionally, the proportion of reagents, a polymer analogue is obtained by reacting with the polymer under conditions of the formation of a covalent bond, which determines the structural units of the polymer present at the end reactions, and convert them to parts by mass using the molar mass values of the structural units. In this regard, complete, that is, 100% conversion of all used monomers or basically all reagents is assumed. In this approach, the sum of the parts by weight represents the total amount of polymer. The polymer content was obtained by dividing the total amount of polymer by the total weight of the batch. In addition to the above-mentioned total amount of polymer, the total mass of the batch therefore includes the reaction medium, optionally cations or anions, and any substance added to the reaction batch that is not expected to be included in the polymer. Substances removed from the reaction mixture (for example, water, which may be distilled, etc.) are discarded.

The total content of primary amino groups and/or amidine groups can be determined using a procedure similar to that described above for polymer content. The molar composition depends on the amounts of monomers used, the degree of hydrolysis determined by analysis, the ratio of amidine groups to primary amino groups determined by ¹³ C-NMR spectroscopy, and, if necessary, the degree of polymer conversion in a polymer-analogous reaction proceeding with the formation of a covalent bond, molar composition structural units of the polymer present at the completion of the reaction. Using the molar mass values of individual structural units, the mole fraction of primary amino groups and/or amidine units can be calculated in mEq. per 1 g of polymer. When determined by ¹³ C-NMR spectroscopy, the signal area of the formate group HCOO- (173 ppm) can overlap with the signal area of the amidine group -N = CH-N- (152 ppm).

K values were determined as described in H. Fikentscher, Cellulosechemie, vol. 13, pp. 48-64 and ss. 71-74, under the conditions specified in each case. The information in parentheses indicates the concentration of the polymer solution calculated based on the polymer and solvent content. Measurements were carried out at 25°C and a pH value of 7.5.

The mass average molecular weight Mw was determined by static light scattering. To do this, the sample was dissolved in 1000 mM saline solution (sodium chloride) at pH 9.0. Mw values were indicated in daltons (Da).

In the examples of polymerization reactions A-2) and hydrolysis A-3) completely demineralized water was used.

A-2) Polymerization reactions

Example P-P1: P1 (polymer VFA=100 mol.%, K-value 90)

N-vinylformamide (234 g) was used as feed stream 1.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (1.2 g) was dissolved in 56.8 g of water at room temperature.

Water (1080.0 g) and 75 wt.% phosphoric acid (2.5 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 2.1 g) was added at 100 rpm until the pH reached 6.6. The initial mixture was heated to 73°C and the pressure in the apparatus was reduced to such an extent that the reaction mixture boiled at 73°C (approximately 350 mbar). Then feed streams 1 and 2 were started simultaneously. At a constant temperature of 73°C, feed stream 1 was supplied for 1 hour and 15 minutes, and feed stream 2 was supplied for 2 hours. After completion of feed stream 2, the reaction mixture was polymerized at 73° C over the next 3 hours. During the entire polymerization and post-polymerization, approximately 190 g of water was distilled off. The mixture was then cooled to room temperature at normal pressure.

A viscous solution of light yellow color was obtained, the solids content of which was 19.7 wt.%, and the polymer content was 19.5 wt.%. The K value of the polymer was 90 (0.5 wt.% aqueous solution). The Mw value was 0.34 million Da. The buffer solution used was expected to provide a pH of 6 to 7.

Example P-P2: P2 (VFA copolymer/acrylate Na=70 mol.%/30 mol.%. K-value 122)

A mixture of water (330 g), 32 wt% aqueous sodium acrylate (217.8 g) adjusted to pH 6.4, and N-vinylformamide (124.2 g) was used as feed stream 1.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (0.3 g) was dissolved in water (66.8 g) at room temperature.

To prepare feed stream 3, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (0.2 g) was dissolved in water (17.4 g) at room temperature.

Water (668.3 g) and 75 wt.% phosphoric acid (1.9 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 3.1 g) was added at 100 rpm until the pH reached 6.6. The initial mixture was heated to 73°C and the pressure in the apparatus was reduced to approximately 340 mbar so that the reaction mixture boiled at 73°C. Feed streams 1 and 2 were then started simultaneously. At a constant temperature of 73°C, feed stream 1 was fed for 2 hours and feed stream 2 for 3 hours. After feed stream 2 was completed, the reaction mixture was post-polymerized at 73°C over the next 2 hours. Feed Stream 3 was then added over 5 minutes and polymerization was continued at 73°C for the next 2 hours. Approximately 190 g of water was distilled off throughout the polymerization and post-polymerization. The mixture was then cooled to room temperature at normal pressure.

A viscous solution of light yellow color was obtained, the solids content of which was 15.9 wt.%, and the polymer content was 15.6 wt.%. The K value of the copolymer was 122 (0.1 wt.% solution in 5 wt.% aqueous NaCl solution). The Mw value was 2.2 million Da.

Example P-P3: P3 (VFA copolymer/acrylate Na=70 mol.%/30 mol.%. Purpose 85)

A mixture of water (240 g), 32 wt.% aqueous sodium acrylate (176.5 g), adjusted to pH 6.4, and N-vinylformamide (100.6 g) was used as feed stream 1.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (5.8 g) was dissolved in water (164.2 g) at room temperature.

To prepare feed stream 3, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (5.8 g) was dissolved in water (164.2 g) at room temperature.

Water (330 g) and 85 wt.% phosphoric acid (1.2 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 4.2 g) was added at 100 rpm until the pH reached 6.6. The initial mixture was heated to 80°C and the pressure in the apparatus was reduced to approximately 450 mbar so that the reaction mixture boiled at 80°C. Feed streams 1 and 2 were then started simultaneously and fed simultaneously for 2 hours. The mixture was then polymerized at 80°C for the next hour. Feed Stream 3 was then added over 5 minutes and polymerization was continued at 80°C for a further 2 hours. Approximately 190 g of water was distilled off throughout the polymerization and post-polymerization. The mixture was then cooled to room temperature at normal pressure.

A viscous solution of light yellow color was obtained, the solids content of which was 16.0 wt.%, and the polymer content was 15.7 wt.%. The K value of the copolymer was 85 (0.5 wt.% solution in 5 wt.% aqueous NaCl solution). The Mw value was 0.8 million Da. The buffer solution used was expected to provide a pH of 6 to 7.

Example P-P4: P4 (VFA copolymer/acrylate Na=70 mol.%/30 mol.%. K-value 152)

To prepare feed stream 1, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (0.4 g) was dissolved in water (81.2 g) at room temperature.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (0.6 g) was dissolved in water (104.7 g) at room temperature.

Water (212 g) was used as feed stream 3.

Water (950 g) and 75 wt.% phosphoric acid (1.4 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 2.5 g) was added at a speed of 100 rpm until the pH reached 6.5. To this buffer solution was added a 32 wt.% aqueous solution of sodium acrylate (144.7 g), the pH of which was adjusted to 6.4, and N-vinylformamide (82.5 g). The initial mixture was heated to 63°C and the pressure in the apparatus was reduced to approximately 230 mbar so that the reaction mixture boiled at 63°C. Then feed stream 1 was supplied for 5 minutes. The mixture was kept at 63°C for 3 hours with continuous distillation of water. The temperature was then raised to 75° C. and the pressure was set to approximately 390 mbar to allow continuous distillation to continue. After 3.5 hours, feed stream 2 was added over 15 minutes. The temperature was then maintained at 75°C for the next 1.25 hours. Feed Stream 3 was then added over 20 minutes, the vacuum was turned off, and the mixture was cooled to room temperature. During the entire polymerization and post-polymerization, approximately 270 g of water was distilled off.

A viscous solution of light yellow color was obtained, the solids content of which was 10.2 wt.%, and the polymer content was 9.9 wt.%. The K value of the copolymer was 152 (0.1 wt.% solution in 5 wt.% aqueous NaCl solution). The Mw value was 4.1 million Da.

Example P-P5: P5 (VFA copolymer/acrylate Na=60 mol.%/40 mol.%. Purpose 90)

A mixture of 32 wt% aqueous sodium acrylate (423.5 g), adjusted to pH 6.4, and N-vinylformamide (155.1 g) was used as feed stream 1.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (2.1 g) was dissolved in water (227.9 g) at room temperature.

Water (573.4 g) and 85 wt.% phosphoric acid (3.0 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 5.2 g) was added at 100 rpm until the pH reached 6.6. The initial mixture was heated to 77°C and the pressure in the apparatus was reduced to approximately 450 mbar so that the reaction mixture boiled at 77°C. Feed streams 1 and 2 were then started simultaneously. At a constant temperature of 77°C, feed stream 1 was supplied for 1.5 hours and feed stream 2 for 2.5 hours. After feed stream 2 was completed, the reaction mixture was post-polymerized at 80°C for the next 2.5 hours. During the entire polymerization and post-polymerization, approximately 200 g of water was distilled off. The mixture was then cooled to room temperature at normal pressure.

A viscous solution of light yellow color was obtained, the solids content of which was 25 wt.%, and the polymer content was 24.5 wt.%. The K value of the copolymer was 90 (0.5 wt.% solution in 5 wt.% aqueous NaCl solution). The Mw value was 0.9 million Da.

Example P-P6: P6 (VFA copolymer/acrylate Na=80 mol.%/20 mol.%. K-value 86)

A mixture of water (293.7 g), 32 wt.% aqueous sodium acrylate (243.0 g), adjusted to pH 6.4, and N-vinylformamide (237.2 g) was used as feed stream 1.

To prepare feed stream 2, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (1.4 g) was dissolved in water (203.6 g) at room temperature.

Water (659.4 g) and 75 wt.% phosphoric acid (3.5 g) were placed in a glass apparatus (2 L) equipped with an anchor stirrer, a downward condenser, an internal thermometer and a nitrogen supply tube. Sodium hydroxide solution (25 wt.%, 6.0 g) was added at 100 rpm until the pH reached 6.6. The initial mixture was heated to 80°C and the pressure in the apparatus was reduced to approximately 460 mbar so that the reaction mixture boiled at 80°C. Then feed streams 1 and 2 were started simultaneously. At a constant temperature of 80°C, feed stream 1 was supplied for 2 hours, and feed stream 2 for 2.5 hours. After feed stream 2 was completed, the reaction mixture was polymerized at 80°C over the next 2.5 hours. During the entire polymerization and post-polymerization, approximately 170 g of water was distilled off. The mixture was then cooled to room temperature at normal pressure.

A viscous solution of light yellow color was obtained, the solids content of which was 21.5 wt.%, and the polymer content was 21.3 wt.%. The K value of the copolymer was 86 (0.5 wt.% solution in 5 wt.% aqueous NaCl solution). The Mw value was 0.7 million Da.

A-3) Hydrolysis of polymers containing vinylformamide in the form of copolymers

Example H-H1P1: H1P1 (VFA[32] polymer derived from polymer P1)

The polymer solution (603.3 g) prepared as described in Example P-P1 was mixed in a 4-neck flask (1 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (8.6 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (94.9 g) was then added. The mixture was kept at 80°C for 3.5 hours. The resulting product was cooled to room temperature and adjusted to pH 3.0 with hydrochloric acid (37 wt.%, 31.7 g).

A viscous solution of light yellow color was obtained with a polymer content of 14.0 wt.%. The degree of hydrolysis of polymerized vinylformamide units was 32 mol%.

Example H-H2P1: H2P1 (VFA[100] polymer derived from polymer P1)

The polymer solution (300.0 g), obtained as described in example P-P1, was stirred in a 4-neck flask (1 L) equipped with an anchor stirrer, an internal thermometer, a dropping funnel and a reflux condenser, with a stirring speed of 80 rpm and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (157.3 g) was then added. The mixture was kept at 80°C for 3 hours. The resulting product was cooled to room temperature and the pH was adjusted to 7 with hydrochloric acid (37%).

A viscous solution of light yellow color was obtained with a polymer content of 7.2 wt.%. The degree of hydrolysis of vinylformamide units was 100 mol.%.

Example H-H3P2: H3P2 (VFA[50] copolymer/Na acrylate=70 mol.%/30 mol.% obtained from copolymer P2)

The polymer solution (1224.3 g) prepared as described in Example P-P2 was mixed in a 4-neck flask (2 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with water (704.4 g) and 40 wt.% aqueous sodium bisulfite solution (8.9 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (140.4 g) was then added. The mixture was kept at 80°C for 5 hours. Then it was cooled to room temperature and the pH was adjusted to 8.5 with hydrochloric acid (37%).

A viscous, slightly opalescent, light yellow solution with a polymer content of 7.1 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 50 mol.%.

Example H-H4P3: H4P3 (VFA[100] copolymer/Na acrylate=70 mol.%/30 mol.% obtained from copolymer P3)

The polymer solution (600.0 g) prepared as described in Example P-P3 was mixed in a 4-neck flask (2 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (4.5 g) and then heated to 80°C. Then a 25 wt.% aqueous sodium hydroxide solution (150.0 g) was added. The mixture was kept at 80°C for 7 hours. The resulting product was cooled to room temperature and the pH was adjusted to 8.5 with hydrochloric acid (37%).

A viscous solution of light yellow color was obtained with a polymer content of 7.7 wt.%. The degree of hydrolysis of vinylformamide units was 100 mol.%.

Example H-H5P3: H5P3 (VFA[51] copolymer/Na acrylate=70 mol.%/30 mol.% obtained from copolymer P3)

The polymer solution (600.0 g) prepared as described in Example P-P3 was mixed in a 4-neck flask (2 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (4.5 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (72.0 g) was then added. The mixture was kept at 80°C for 3.5 hours. The resulting product was cooled to room temperature and the pH was adjusted to 8.5 with hydrochloric acid (37%).

A viscous, slightly opalescent, light yellow solution with a polymer content of 10.4 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 51 mol.%.

Example H-H6P3: H6P3 (VFF[30] copolymer/Na acrylate=70 mol.%/30 mol.% obtained from copolymer P3)

The polymer solution (600.0 g) prepared as described in Example P-P3 was mixed in a 4-neck flask (2 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (4.5 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (45.5 g) was then added. The mixture was kept at 80°C for 7 hours. The resulting product was cooled to room temperature and the pH was adjusted to 8.5 with hydrochloric acid (37%).

A viscous, slightly opalescent, light yellow solution with a polymer content of 11.7 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 30 mol.%.

Example H-H7P4: H7P4 (VFA[511/Na acrylate=70 mol%/30 mol% copolymer obtained from copolymer P4)

The polymer solution (159.8 g) prepared as described in Example P-P4 was mixed in a 4-neck flask (500 ml) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (0.7 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (11.8 g) was then added. The mixture was kept at 80°C for 4.5 hours. The resulting product was diluted with water (71.4 g) and cooled to room temperature. The pH was adjusted to 4.7 with hydrochloric acid (37%).

A viscous, slightly opalescent, light yellow solution with a polymer content of 5.0 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 51 mol.%.

Example H-H8P5: H8P5 (VFA[100] copolymer/Na acrylate=60 mol.%/40 mol.% obtained from copolymer P5)

The polymer solution (1102.9 g) prepared as described in Example P-P5 was mixed in a 4-neck flask equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser at a stirring speed of 80 rpm with 40 wt. % aqueous sodium bisulfite solution (10.5 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (355.6 g) was then added. The mixture was kept at 80°C for 7 hours and then cooled to room temperature and adjusted to pH 8.5 with hydrochloric acid (37%).

A viscous, slightly opalescent solution with a polymer content of 11.5 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 100 mol.%.

Example H-H9P6: H9P6 (VFF[35] copolymer/Na acrylate=80 mol.%/20 mol.% obtained from copolymer P6)

The polymer solution (600.0 g) prepared as described in Example P-P6 was mixed in a 4-neck flask (2 L) equipped with an anchor stirrer, internal thermometer, dropping funnel and reflux condenser, with a stirring speed of 80 rpm with 40 wt.% aqueous sodium bisulfite solution (4.5 g) and then heated to 80°C. A 25 wt% aqueous sodium hydroxide solution (83.3 g) was then added. The mixture was kept at 80°C for 3.5 hours. The resulting product was cooled to room temperature and the pH was adjusted to 8.5 with hydrochloric acid (37%).

A viscous, slightly opalescent, light yellow solution with a polymer content of 15.3 wt.% was obtained. The degree of hydrolysis of vinylformamide units was 35 mol.%.

A-4) General information about the obtained individual polymers

Notes:

a) the amount of non-hydrolyzed N-CHO groups in the N-vinylformamide used in the polymerization was calculated based on the amount of N-vinylformamide used in the polymerization minus the amount of hydrolyzed N-CHO groups in the N-vinylformamide used in the polymerization,

b) the amount of hydrolyzed N-CHO groups in the N-vinylformamide used in the polymerization was calculated based on the amount of N-vinylformamide used in the polymerization and the determined degree of hydrolysis,

c) the amount of sodium acrylate polymerized was calculated based on the amount of sodium acrylate used in the polymerization.

B) Preparation of sprayable suspensions or sprayable solutions

To obtain sprayable suspensions or sprayable solutions, the corresponding aqueous solutions described in the examples, containing said polymer and, if necessary, said starch, were added as a solid with stirring to a glass vessel, marked at the 4 L level, in which potable water was already present (2 l). For this purpose, in the case of the aqueous solutions described in the examples containing the said polymer, such an amount of said aqueous solution was added to add 20 g of polymer or, in the case of combination with starch, 10 g of polymer based on the polymer content. In the case of combination with starch, 10 g of starch was added based on the starch solids content. After addition was complete, the slurry was stirred or dissolved. Then drinking water was added to the 4 liter mark on the neck of the vessel. The preparation of pure starch suspension is described below. The reference solution containing no additives (=L(0) in Table B1) consisted only of drinking water. The compositions of sprayed solutions L are given in table. B1, and the compositions of sprayed suspensions S are given in table. AT 2.

Example S-St1: St1 (concentration)

A starch suspension from Cargill commercial starch, size 35802 (Cargill cationic starch, powder, insoluble/partially soluble in water) was prepared by suspending 20 g of the starch solid powder in 2 L of drinking water at room temperature and then diluting with drinking water to total volume 4 l. The starch concentration in the aqueous suspension was 5 g/L based on solids content. The pH value of the aqueous suspension was 7.3.

Notes:

a) comparison,

b) according to the present invention,

c) concentration based on the polymer content in an aqueous solution, as described in the example.

Notes:

a) comparison,

b) according to the present invention,

c) concentration based on the polymer content in the aqueous suspension, as described in the example.

C) Paper

C-1) Physical characteristics Determination of dry matter content

To determine the solids content (TG), the wet mass (MF) obtained from the wet paper sample was determined on a calibrated high-speed top-pan balance that can be used for weighing to the nearest 0.01 g. The area of the wet paper sample was preferably at least 10 cm × 10 cm. The wet paper sample was then placed in a calibrated oven that maintained the set temperature to within ±2°C and dried to constant weight at a set temperature of 105°C. as a rule, it took 90 minutes. The still warm sample of dried paper was then transferred to a desiccator which contained a suitable drying agent such as silica gel. After cooling to room temperature, the mass of the dried paper sample (MT) was determined on the above-mentioned scales. The dry matter content in the paper sample was calculated using the formula: TG=100 × MT/MF and expressed in wt.%. In most cases, percentages were given to the first decimal place. If this percentage value did not change when rounded to the first decimal place, this indicated that constant weight had been achieved at a dry matter content of 1 to 100 wt%. When the dry matter content was from 0 to less than 1 wt.%, the corresponding indicator was the percentage value rounded to the second decimal point. Drying was carried out at atmospheric pressure, possibly at 101.32 kPa, without correction for weather and altitude. During the drying process, the atmospheric pressure normally prevailing in the environment was maintained, possibly at 101.32 kPa. No correction was made for minor changes in atmospheric pressure due to weather and altitude. In the case of a wet sample that had not yet reached the consistency of paper, such as a paper pulp slurry or paper pulp, the wet sample was dried on an appropriate bowl with a larger surface area.

Internal adhesion strength of the resulting dried paper web

The resulting dried paper web was tested after storage in an artificial climate chamber at a constant temperature of 23°C and a humidity of 50% for 12 hours. The internal adhesion strength test was carried out according to the method according to the rules of the Technical Association of the Pulp and Paper Industry (Tappi) T833 pm- 94. 10 Strips of paper 2.5 cm wide and 12.7 cm long were cut from two sheets of A4 paper, which were previously obtained from the dried paper web of a paper machine. Each individual paper sample was attached to a separate backing and metal bracket using double-sided tape. The metal bracket was subjected to impacts from a pendulum arm, causing the test paper sample to split in a direction parallel to the surface of the paper. The energy required for this process was measured. The apparatus used for measurement was an internal bond strength tester from TMI (Testing Machines Inc., Islandia, New York, USA). We used 3M double-sided tape (width 25.4 mm, tape type No. 140). The measuring device provided the energy (J/m ² ) required to split the paper sample over a standardized area. The average value was obtained from 10 individual measurements.

C-2) Obtaining raw paper material

Paper pulp, which served as a raw material for making paper, was obtained by treating the paper pulp in a pulp breaker. The mass was obtained by dissolving it in drinking water and mechanically processing the paper webs in a cellulose breaker to a dry matter content of approximately 3.5-4 wt.%. Typically, the fineness of paper pulp measured on a Schopper Riegler was around 50°SR. The paper webs were a packaging base paper meeting the technical specification "Testliner 2", characterized by a paper weight of 120 g/m ² , produced by Thurpapier (Weinfelden, Switzerland).

C-3) Obtaining paper when processing wet paper webs with spraying

The resulting paper consisted of two layers: a top layer with a density of 40 g/m ² and a base with a density of 80 g/m ² . This paper was produced on a test paper machine from the Paper Technology Foundation (PTS, Heidenau). To produce two-ply paper, the test paper machine was equipped with a pulp distributor for the bottom grid and an additional pulp distributor for the top grid. The paper pulp was diluted with drinking water so that the dry matter content was 0.35 wt.%. Then the paper pulp was pumped into two pulp distributors, from where it was directed to the upper mesh in the form of a sieve and to the lower mesh in the form of a sieve. The top sieve and the base sieve moved towards each other at an angle of 60° and formed a narrow gap at the end. Contacting the top layer with the underlying layer after passing the gap provided sufficient adhesion to separate the paper layers from the screens. The loosely adhered layers were then sent to the pressing section, where they were pressed on the opposite side of the screens in the press section of the paper machine, that is, pressed together during dehydration. The resulting paper web was then passed through the heated cylinders of the drying section, where temperatures reached up to 100°C, and the dried paper was rolled at the end of the drying section. The dry solids content of the resulting dried paper was typically 93-94 wt.% for the type of structure described above, the density indicated and the paper machine speed of 0.85 m ² /min. The contact pressure in the pressing section can be varied to provide different dry matter contents after passing through the pressing section. Depending on the contact pressure in the test paper machine, the solids content ranged from 40 wt.% to 52 wt.%. The solids content before the press can be varied by using a chemical desiccant and/or by applying a vacuum to the undersides of the upper and lower screens. As a result, the solids content before the press of the test paper machine varied in the range from 15 wt.% to 22 wt.%.

Three sets of parameters were used:

1. Parameter set "B", which was the basic parameter set, included a measured amount of retention additive (Percol 540, RTM BASF, cationically modified polyacrylamide, emulsified in hydrocarbons and water, density approximately 1 g/cm ³ , pH value 3-6 , cream color, solids content 44 wt.%), which was extremely low and corresponded to approximately 100 g of solids in the retention additive per ton of the entire web from top layer to bottom layer (0.01 wt.%). The same relative amount of the same retention additive was measured into the top and bottom layers. Under these conditions, the solids content before the press was approximately 15.8 wt.%.

2. The "V" parameter set, where vacuum was used, included a retention additive, and the amount of retention additive remained constant at 100 g per ton of paper, as above for the parameter set of claim 1. However, at the bottom surface of the corresponding screen after two pulp distributors created additional vacuum. The vacuum was created in such a way as to ensure a sufficient size of the required effects without disturbing the emerging structure. This situation corresponded to the installation of a vacuum, which in this case ensured that the dry matter content of the wet paper web before the press was approximately 18.2 wt.%.

3. The "R" parameter set, where an additional retention additive was used, included turning off the vacuum after setting the parameters in paragraph 2. The amount of retention additive in the parameter set in paragraph 1 was increased to approximately 370 g of retention additive per ton of paper in the total substance composition ( 0.037 wt.%). The dry matter content of the wet paper webs before the press reached approximately 18.2 wt.%, which coincided with the value previously achieved when using a vacuum according to claim 2.

When spraying wet paper webs with spray solutions or spray suspensions, the spray solution or spray suspension is sprayed through a nozzle until the top and bottom layers contact ("BP" = "before press"). For this purpose, a two-fluid nozzle from Schlick was used. Spraying was carried out before the pressing section. The nozzle was located at a distance of approximately 15 cm from the bonding line, that is, the pressing line with dehydration in the pressing section. Thus, the distance to the top of the paper stack on the sieve was approximately 35 cm. The pressure required to open the nozzle valve and spray the spray solution or suspension was 1 bar. The spray width for uniform coverage was 35 cm. However, when processing sheets of dried paper for further analysis, 5 cm along the edge was not taken into account. The spray solution or spray suspension was sprayed in two different application quantities. The first amount was in the range of about 0.1 l/m ² , which corresponded to an applied amount of 0.5 g/m ² at a concentration of approximately 5 g/l. The second amount was in the range of about 0.2 l/m ² , which corresponded to an applied amount of 1.0 g/m ² at a concentration of approximately 5 g/l. Due to the high dilution, the density of the spray solution or spray suspension was assumed to be approximately 1 g/cm ³ .

C-4) Testing and determining the properties of the resulting dried paper

The dried paper was produced on a paper machine as described in Example C-3), using the concentration of the spray solution or spray dispersion and the parameters indicated in Table. C1 - table C3,. In table SV1 table C3 also presents the measured values of the internal bond strength of the tested dried paper stocks, as described in Example C-1).

Notes:

a) comparison,

b) according to the present invention.

When compared with comparison examples, the data presented in table. C1, indicate that the paper obtained by spraying the solutions of the present invention is characterized by significantly increased internal adhesion strength. Moreover, increasing the solids content after the wire section due to negative pressure or increased amount of retention polymer in the paper produced using the spray solutions of the present invention leads to a further increase in internal bond strength, although these quantities have a negligible and inconsistent effects on paper properties from comparison examples.

Notes:

a) comparison,

b) according to the present invention.

The data presented in table. C2, indicate that even when the application amount is doubled, the paper produced by spraying the solutions of the present invention exhibits significantly increased internal bond strength compared to the paper samples in the comparative examples. Increasing the solids content downstream of the screen section, either by negative pressure or by increasing the amount of retention polymer, almost always results in a further increase in the internal bond strength of the paper produced by spraying the solutions of the present invention, although these quantities have a small and inconsistent effect. comparison examples.

Notes:

a) comparison,

b) according to the present invention.

From the data presented in table. C3, as in table. C1 and table. C2, it can be seen that the paper produced using the sprayable dispersions of the present invention exhibits significantly improved internal bond strength compared to the comparative examples. Increasing the solids content after the wire section due to negative pressure or increased amount of retention polymer in the paper produced using the sprayable suspensions of the present invention leads to a further increase in internal bond strength, although these quantities have a small and inconsistent effect on properties of paper from comparison examples. When compared with table. C1 data presented in table. C3 indicate that replacing half of the polymers used with cationic starch does not further increase the internal adhesion strength of a paper sample of the same size.

Claims (51)

1. A method for producing dried multilayer paper, including the following stages: (A) dehydrating the first aqueous fibrous suspension in which the solids content is from 0.1 wt.% to 6 wt.% on the first screen, thereby obtaining a first fibrous web in which the dry matter content is from 14 wt.% up to 25 wt.%, (B) dehydrating a second aqueous fibrous suspension in which the solids content is from 0.1 wt.% to 6 wt.% on the second screen, thereby obtaining a second fibrous web in which the solids content is from 14 wt.% up to 25 wt.%, (C) spraying the first fibrous web, the second fibrous web, or the first fibrous web and the second fibrous web on at least one side of the surface with a spray solution or spray suspension, thereby producing at least one sprayed fibrous web that contains a side sprayed surfaces, (D) connecting the first fibrous web to a second fibrous web, of which at least one of the two webs is a sputtered fibrous web, such that at least one side of the sputtered surface of the two fibrous webs forms a side of the surface in contact with the other fibrous web, and the fibrous webs lie one above the other over the entire width, thereby creating a layered material, (E) dehydrating the laminate by pressing, thereby forming a partially dehydrated laminate, (F) dehydrating the partially dehydrated laminate by applying heat to form a dried laminate paper, wherein the solution to be sprayed or the suspension to be sprayed contains (s-a) water, (c-c) at least one water-soluble polymer P, which can be obtained by polymerization (i) from 40 to 85 mol.% of the monomer of formula I where R ¹ means H or C ₁ -C ₆ alkyl, (ii) from 15 to 60 mol.% of one or more ethylenically unsaturated monomers, which differ from the monomer of formula I, where the total amount of all monomers (i) and (ii) is 100 mol.%, where the proportion of water is at least 75 wt.% based on the sprayed solution or sprayed suspension. 2. The method according to claim 1, wherein in step (E) the solids content of the partially dehydrated laminate is from 35 wt.% to 65 wt.%. 3. The method according to any one of claims 1 or 2, where the polymer P, which is obtained by polymerization (i) from 40 to 85 mol.% of the monomer of formula I, (ii) from 15 to 60 mol.% of one or more ethylenically unsaturated monomers other than the monomer of formula I, wherein one or more ethylenically unsaturated monomers are selected from (ii-1) acrylic acid or methacrylic acid or their alkali, alkaline earth metal or ammonium salts, (ii-2) acrylonitrile or methacrylonitrile, (ii-3) vinyl acetate, (ii-4) monoethylenically unsaturated sulfonic acid, monoethylenically unsaturated phosphonic acid, monoethylenically unsaturated phosphoric acid mono- or diester or monoethylenically unsaturated carboxylic acid containing from 4 to 8 carbon atoms, which is different from methacrylic acid, or their alkali, alkaline earth metal or ammonium salts, (ii-5) a quaternized monoethylenically unsaturated monomer, a monoethylenically unsaturated monomer that contains at least one secondary or tertiary amine group and in which at least one secondary or tertiary amine group is protonated at pH 7, or a diallyl-substituted amine that contains only two ethylene double bonds and is quaternized or protonated at pH 7, or their salt form, (ii-6) a monoethylenically unsaturated monomer containing no charge at pH 7 and different from acrylonitrile, methacrylonitrile and vinyl acetate, or an ethylenically unsaturated monomer only two of whose ethylenic double bonds are conjugated and uncharged at pH 7, (ii-7) from 0 to 2 mol.% of a monomer containing at least two ethylenically unsaturated double bonds that are not conjugated and that are different from a diallyl-substituted amine that contains only two ethylenic double bonds, (ii-8) from 0 to 10 mol.% ethylenically unsaturated monomer different from monomers (ii-1) - (ii-7), where the total amount of all monomers (i) and (ii-1)-(ii-8) is 100 mol.% and the mole percentages refer to the total amount of all monomers (i) and (ii-1)-(ii-8), and optionally by subsequent partial or complete hydrolysis of monomer units of formula (I) which polymerize to polymer P to form primary amino groups or amidine groups, these groups also being partially or completely hydrolyzed in the presence of polymerizable vinyl acetate units. 4. Method according to any one of paragraphs. 1-3, where one or more ethylenically unsaturated monomers contains (ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali, alkaline earth metal or ammonium salts and/or (ii-2) from 0 to 35 mol.% acrylonitrile or methacrylonitrile and/or, (ii-3) from 0 to 35 mol.% vinyl acetate and/or, (ii-4) from 0 to 10 mol.% monoethylenically unsaturated sulfonic acid, monoethylenically unsaturated phosphonic acid, monoethylenically unsaturated phosphoric acid mono- or diester or monoethylenically unsaturated carboxylic acid containing from 4 to 8 carbon atoms, which is different from methacrylic acid, or salts thereof alkali, alkaline earth metals or ammonium and/or, (ii-5) from 0 to 20 mol.% quaternized monoethylenically unsaturated monomer, quaternized monoethylenically unsaturated monomer which contains at least one secondary or tertiary amine group, in which at least one secondary or tertiary amine group is protonated at pH 7, or diallyl-substituted amine, which contains only two ethylene double bonds and is quaternized or protonated at pH 7, or a salt form thereof and/or, (ii-6) from 0 to 35 mol.% of a monoethylenically unsaturated monomer containing no charge at pH 7 and other than acrylonitrile, methacrylonitrile and vinyl acetate, or an ethylenically unsaturated monomer, only two of whose ethylenic double bonds are conjugated and uncharged at pH 7, and which is different from acrylonitrile, methacrylonitrile and vinyl acetate and/or, (ii-7) from 0 to 1 mol.% of a monomer containing at least two ethylenically unsaturated double bonds that are not conjugated and that are different from a diallyl-substituted amine that contains only two ethylenic double bonds and/or, (ii-8) from 0 to 5 mol.% ethylenically unsaturated monomer, different from monomers (i) and (ii-1)-(ii-7), where the mole percentages refer to the total amount of all monomers used for polymerization, and the total amount of all monomers is 100 mol%. 5. Method according to any one of paragraphs. 1-4, where polymer P is obtained by polymerization (i) from 50 to 85 mol.% of the monomer of formula I, (ii-1) from 15 to 50 mol.% acrylic acid or methacrylic acid or their alkali, alkaline earth metal or ammonium salts, (ii-2) from 0 to 35 mol.% acrylonitrile or methacrylonitrile, where the total amount of all monomers (i) and (ii-1)-(ii-2) is 100 mol.% and the mole percent refers to the total amount of all monomers (i) and (ii-1)-(ii-2), and optionally by subsequent partial or complete hydrolysis of the monomer units of formula (I), which polymerize to polymer P to form amino groups or amidine groups. 6. Method according to any one of paragraphs. 1-5, wherein an organic polymer (a-c) is preferably added as a retaining agent to the first aqueous fibrous suspension containing water (a-a) and the first fibrous material (a-b) before dehydration in step (A), and to the second aqueous fibrous suspension containing water (b-a) and the second fibrous material (b-b), an organic polymer (b-c) is added as a retaining agent before dehydration in step (B). 7. The method according to claim 6, where the amount of added organic polymer (a-c) is from 0.001 wt.% to 0.2 wt.% based on the first fibrous material (a-b), and the amount of added organic polymer (b -c) is from 0.001 wt.% to 0.2 wt.% based on the second fibrous material (b-b). 8. Method according to any one of paragraphs. 1-7, wherein in step (C) the first fibrous web and the second fibrous web are sprayed to form at least two sprayed fibrous webs, and in step (D) the first fibrous web is joined to the second fibrous web in this manner such that the surface-sprayed side of the first fibrous web forms a surface contact side with the second fibrous web, and the surface-sprayed side of the second fibrous web forms a surface contact side with the first fibrous web. 9. Method according to any one of paragraphs. 1-8, wherein polymer P can be obtained by further subsequent partial or complete hydrolysis of monomer units of formula (I), which polymerize to form polymer P and to form primary amino groups or amidine groups. 10. A paper machine, the equipment of which includes a first wire section with a first screen that contains a first wire top side and a first screen bottom side, and a second screen section with a second screen that contains a second screen top side and a second screen bottom side, a spray device, a pressing section and a drying section with heated cylinders, and these equipments are arranged in the paper machine in the following order: a first wire section and a second wire section, followed by a spraying device, then a pressing section and a drying section, wherein the spraying device contains a spray solution or a spray suspension as defined in one of paragraphs. 1-5, and the paper machine is suitable for the method according to claim 1.