Processing systems for the manufacture of paper, board or the like

Abstract

The present invention relates to a chemical treatment system for making paper, cardboard or the like, and to a method for using the same. The system comprises a first component, which is a glyoxylated polyacrylamide having a net cationic charge density and obtained by glyoxylation of a cationic polyacrylamide base polymer having a weight-average molecular weight (MW) in the range of 30,000-500,000 g / mol. The system also comprises a second component, which comprises a mixture of at least a high-branched starch and an anionic first polymer having a weight-average molecular weight (MW)>200,000 g / mol. When measured at pH 2.8, the second component has a net cationic charge density in the range of 0.05 meq / g to 0.9 meq / g, and when measured at pH 7, has a net anionic charge density in the range of 2 meq / g to 0.1 meq / g.

Description

Technical Field

[0001] The present invention relates to a chemical treatment system for the manufacture of paper, board or the like according to the preambles of the accompanying independent claims. Background Art

[0002] In paper and paperboard manufacturing, various chemical additives are added to the fiber stock before forming the paper or paperboard web to modify the properties of the fiber stock and, ultimately, the paper or paperboard. Dry strength is often a desired property of the final paper or paperboard. Strength properties are of particular concern when the paper or paperboard is made from recycled fibers. Recycled fibers typically have lower strength properties than virgin fibers. Due to increasing consumer awareness and overall concern for sustainability, the level of recycled fiber in paper and paperboard manufacturing is increasing, leading to a rise in the amount of recycled fiber with low or very low strength properties in the fiber stock. At the same time, the degree of recycling of individual fibers is increasing, meaning the same fibers are being recycled more and more times. This leads to deterioration in the properties of the recycled fibers, including decreasing fiber length and fiber keratinization, which in turn leads to poorer properties of the resulting fiber web, particularly strength properties. This deterioration in properties can be counteracted by the use of chemical additives.

[0003] Synthetic polymers are commonly used additives in papermaking to improve the strength properties of the final paper or board. Polymers can be added to the fiber stock, where they interact with stock components (e.g., fibers) and improve the properties of the final fiber web. However, recycled fibers, in particular, do not always provide optimal interaction with the added polymers. In cases where the fiber surface charge is low, for example, due to extensive recycling and repulping, the interaction between the added polymer and the fibers is not strong, as expected. Furthermore, interfering substances can accumulate in the circulating water used to prepare the fiber stock, potentially interfering with the interaction between the polymer and the fibers. Therefore, there is a continuing need for new and effective substances, compositions, or combinations that can be used to improve the strength properties of produced paper and board, particularly when using increasing amounts of recycled fibers. Summary of the Invention

[0004] The object of the present invention is to minimize or even eliminate the drawbacks present in the prior art.

[0005] It is also an object of the present invention to provide a chemical treatment system which provides an effective improvement in the dry strength properties of the final paper or board.

[0006] It is also an object of the present invention to provide a chemical treatment system that improves the dry strength properties of paper and paperboard produced by using recycled fibers.

[0007] These objects are achieved by the present invention having the features given below in the characterizing part of the independent claim.Some preferred embodiments are disclosed in the dependent claims.

[0008] Where applicable, the embodiments mentioned herein relate to all aspects of the invention, the processing system, the use thereof and the method for producing paper, board or the like, even if this is not always mentioned separately.

[0009] A typical chemical processing system for making paper, paperboard or the like according to the present invention comprises

[0010] a first component, which is a glyoxylated polyacrylamide having a net cationic charge density and is obtained by glyoxylation of a cationic polyacrylamide base polymer having a weight average molecular weight MW in the range of 30,000 to 500,000 g / mol, and

[0011] - A second component comprising a mixture of at least

[0012] - high in amylopectin, and

[0013] - an anionic first polymer having a weight average molecular weight of >200000 g / mol,

[0014] wherein the second component has a net cationic charge in the range of 0.05 meq / g to 0.9 meq / g when measured at pH 2.8, and a net anionic charge in the range of -2 meq / g to -0.1 meq / g when measured at pH 7.

[0015] A typical use of a chemical treatment system according to the invention, comprising the first component and the second component according to the invention, is for improving the strength properties of paper, board or the like by adding the chemical treatment system to a fiber stock.

[0016] A typical method for manufacturing paper, paperboard or the like according to the present invention comprises

[0017] - obtaining a fiber stock comprising cellulose fibers,

[0018] - adding a chemical treatment system according to the invention and comprising a first component and a second component to the fiber stock, wherein the first component and the second component are added to the fiber stock in the form of aqueous solutions.

[0019] It has now been surprisingly found that when a chemical treatment system comprising a first component and a second component as defined in the present invention is used together, an unexpected improvement in the strength properties of the final paper, paperboard or the like is obtained, particularly when the fiber stock comprises recycled fibers. The reasons for this surprising result are not yet fully understood, but it is speculated that the high molecular weight of the glyoxylated polyacrylamide base polymer in the first component can provide an effective and far-reaching interaction with the ingredients of the second component. It is speculated that a large number of various bonds are formed between the first component and the second component of the chemical treatment system and between the fiber stock components, which also contributes to the strength improvement. Even without a complete theoretical explanation, it has been observed that the present invention provides strength enhancement, such as SCT strength enhancement, which significantly exceeds expectations.

[0020] It has been observed that the chemical treatment system according to the present invention provides a strength enhancement for the final paper, board or the like when the zeta potential value of the fiber stock is close to zero, for example, -15 mV to -1 mV, preferably -12 mV to -2 mV, which is usually the case for fiber stock containing recycled fibers. The chemical treatment system is able to successfully interact with the (recycled) fibers even if their surface charge is low, as indicated by the zeta potential value of the fiber stock.

[0021] The first and second components of the chemical treatment system according to the present invention can be added separately and preferably continuously to the fiber stock. According to a preferred embodiment, the first and second components are added separately and continuously to a thick fiber stock having a consistency of at least 2% by weight (e.g., 2-6% by weight), calculated on dry fiber. More preferably, the first component is added to the fiber stock before the second component. The time interval between the addition of the first and second components is preferably long enough to ensure effective mixing of the first component with the stock before the addition of the second component.

[0022] The first component of the chemical treatment system is a glyoxylated polyacrylamide having a net cationic charge density. The first component is in the form of an aqueous solution and can have a solids content of 3-7% by weight and can be added to the fiber stock in this form. The glyoxylated polyacrylamide is obtained by glyoxylation of a cationic polyacrylamide base polymer. According to a preferred embodiment, the glyoxylation of the base polymer is carried out as an on-site glyoxylation, preferably as an on-site glyoxylation of an aqueous base polymer composition at a paper mill or board mill. The glyoxylated polyacrylamide produced on-site at the paper mill or board mill is usually used immediately or at least within the next 1-3 days after on-site production. The resulting glyoxylated polyacrylamide having a net cationic charge density can be used directly in the chemical treatment system of the present invention with or without further dilution.

[0023] Based on the total weight of glyoxal and polyacrylamide base polymer, a glyoxalated cationic polyacrylamide particularly suitable for use as the first component of the chemical treatment system of the present invention can be obtained by reacting the cationic polyacrylamide base polymer with 4-25 wt %, preferably 8-15 wt % of glyoxal. Glyoxal effectively reacts with the cationic polyacrylamide base polymer. The resulting glyoxalated polyacrylamide provides effective interactions with both fibers, particularly recycled fibers, and the components of the second component of the chemical treatment system, for example, providing cationic sites in the form of ionic bonds. The increased interactions and bond formation are believed to improve observed ultimate strength.

[0024] The cationic polyacrylamide base polymer of the glyoxylated polyacrylamide of the first component can be obtained by polymerization of acrylamide and at least one cationic monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), 3-(acrylamidopropyl)trimethylammonium chloride (APTAC) and 3-(methacrylamidopropyl)trimethylammonium chloride (MAPTAC). These cationic monomers provide hydrolytic stability to the cationic polyacrylamide base polymer.

[0025] The cationic polyacrylamide base polymer may comprise at least 10 mol% of a cationic monomer. According to one embodiment, the cationic polyacrylamide base polymer of the first component may be obtained by polymerization of 10-50 mol%, preferably 10-30 mol%, more preferably 15-25 mol% of a cationic monomer, preferably selected from the monomers defined above. The relatively high amount of cationic monomers used in the polyacrylamide base polymer provides effective interaction with the anionic second component of the fiber and the chemical treatment system. When the first component is added to the fiber stock, it can even provide a fiber stock with a positive zeta potential. This provides more possible binding sites (e.g., for ionic bond formation) for the ingredients of the second component.

[0026] According to the present invention, the first component of the chemical treatment system is a glyoxylated polyacrylamide obtained by glyoxylation of a cationic polyacrylamide base polymer, having a weight-average molecular weight in the range of 30,000-500,000 g / mol. According to a preferred embodiment of the present invention, the cationic polyacrylamide base polymer may have a weight-average molecular weight in the range of 40,000-400,000 g / mol, preferably 80,000-200,000 or 100,000-150,000 g / mol. The high weight-average molecular weight of the cationic polyacrylamide base polymer provides a large molecular size for the glyoxylated polyacrylamide of the first component. As described above, the large molecular size of the first component can provide improved strength properties for the final paper or paperboard. The number-average molecular weight of the polyacrylamide base polymer may be 5,000 g / mol, preferably 10,000 g / mol, more preferably 15,000 g / mol, to 100,000 g / mol or less, preferably to 75,000 g / mol or less, more preferably to 50,000 g / mol or less.

[0027] The second component of the chemical treatment system of the present invention is a mixture of at least high-branched starch and a first polymer. Before the second component is added to the fiber stock, the high-branched starch and the first polymer are preferably mixed with each other. When mixed, the high-branched starch and the first polymer form a complex with an optimal spatial configuration and a charge for interacting with the first component and the fiber, particularly the recycled fiber. Therefore, when added to the fiber stock, the second component is preferably in the form of a single aqueous solution. During mixing, the high-branched starch is in solution and the first polymer is in dispersion. For example, the second component can be obtained by effectively mixing a starch solution into a dispersion of the first polymer.

[0028] When measured at pH 2.8, the second component of the chemical treatment composition may have a net cationic charge density in the range of 0.05 meq / g to 0.9 meq / g, preferably 0.07-0.7 meq / g, more preferably 0.1-0.3 meq / g, and when measured at pH 7, a net anionic charge in the range of -2 meq / g to -0.1 meq / g. Charge density is measured using a Particle Charge Detector, Mutek PCD03. When measured at pH 7.0, the second component of the treatment composition may preferably have a net anionic charge density in the range of -2 meq / g to -0.4 meq / g, preferably -1.5 meq / g to -0.5 meq / g. These defined net charge densities provide for easy handling of the second component during its manufacture while ensuring that sufficient anionic charge is present to provide effective interaction with the first component of the treatment system.

[0029] According to one embodiment of the present invention, the second component of the treatment system comprises high branched starch, preferably cationic high branched starch. Based on the total dry weight of starch, the high branched starch can have a branched starch content of ≥90 wt%, preferably ≥95 wt%, and sometimes more preferably ≥98 wt%. The first polymer can be a cationic high branched starch selected from potato, waxy potato, rice, corn, waxy corn, wheat, barley, sweet potato or cassava starch. Preferably, the high branched starch is a cationic waxy starch, for example, cationic waxy corn starch or cationic waxy potato starch. The high branched starch is in the form of an aqueous solution, which means that the high branched starch has been dissolved in water, for example, by cooking. Cooking can be carried out at a temperature of 60-135°C. The dissolved high branched starch does not contain starch granules, granules and / or specific starch structures.

[0030] According to a preferred embodiment, the second component comprises a highly branched starch which is a cationic non-degradable highly branched starch. In the context of the present invention, this means a highly branched starch which has been modified solely by cationization and is non-degradable and non-crosslinked. According to one embodiment of the present invention, the highly branched starch of the second component may be a cationic non-degradable highly branched starch which comprises at least 70% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, more preferably at least 90% by weight, sometimes more preferably at least 95% by weight of starch units having an average molecular weight MW of greater than 20,000,000 g / mol, preferably greater than 50,000,000 g / mol, more preferably greater than 100,000,000 g / mol, sometimes even greater than 200,000,000 g / mol.

[0031] High branched starch can be cationized by any suitable method. Preferably, starch is cationized by using 2,3-epoxypropyltrimethylammonium chloride or 3-chloro-2-hydroxypropyltrimethylammonium chloride, preferably 2,3-epoxypropyltrimethyl-ammonium chloride. It is also possible to cationize high branched starch by using cationic acrylamide derivatives such as (3-acrylamidopropyl)-trimethylammonium chloride. Cationic high branched starch can have a degree of substitution of 0.025-0.3, preferably 0.03-0.16, more preferably 0.045-0.1. The degree of substitution is relative to the cationic degree of the high branched starch.

[0032] The second component may comprise the highly amylopectin starch in an amount of 20-80 wt%, preferably 30-60 wt%, based on the total dry weight of the second component.

[0033] The second component of the chemical treatment system further comprises an anionic first polymer which may be selected from carboxymethylcellulose or from neat anionic copolymers of (meth)acrylamide.

[0034] According to a preferred embodiment, the anionic first polymer of the second component is an anionic carboxymethyl cellulose. The anionic carboxymethyl cellulose may have a weight average molecular weight (MW) of at least 200,000 g / mol, preferably at least 250,000 g / mol, more preferably at least 300,000 g / mol or at least 350,000 g / mol. The weight average molecular weight (MW) may be in the range of 200,000-1,000,000 g / mol, preferably 250,000-900,000 g / mol, more preferably 300,000-750,000 g / mol, more preferably 350,000-550,000 g / mol.

[0035] The carboxymethyl cellulose may have a carboxymethyl degree of substitution of ≥0.4, preferably ≥0.5, more preferably ≥0.6. The carboxymethyl degree of substitution may be 0.4-1.0, preferably 0.5-0.9, thereby providing excellent water solubility. When measured at pH 7, the carboxymethyl cellulose may have a charge density value of <-1.1 meq / g, preferably in the range of -1.6 meq / g to -4.7 meq / g, more preferably -2.1 meq / g to -4.1 meq / g, more preferably -2.5 meq / g to -3.8 meq / g. All measured charge density values ​​are calculated by weight as dry weight.

[0036] According to a preferred embodiment, the first polymer of the second component can be obtained by polymerization of (meth)acrylamide and at least one anionic monomer, the anionic monomer being selected from unsaturated monocarboxylic acids or dicarboxylic acids or their salts, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, isocrotonic acid and any mixture thereof. Therefore, the anionic first polymer can be a net anionic copolymer of (meth)acrylamide. The net anionic copolymer of (meth)acrylamide can be an anionic copolymer of (meth)acrylamide, which only comprises polymer units of anionic monomers derived from (meth)acrylamide monomers. Alternatively, the net anionic copolymer of (meth)acrylamide can be a net anionic amphoteric copolymer of (meth)acrylamide, which comprises polymer units derived from anionic monomers, cationic monomers and (meth)acrylamide monomers, as long as the anionic charge exceeds the cationic charge in the copolymer. The net anionic copolymer of (meth)acrylamide can have a weight average molecular weight MW of at least 200,000 g / mol, preferably at least 500,000 g / mol. The weight average molecular weight MW may be in the range of 200,000-20,000,000 g / mol, preferably 500,000-10,000,000 g / mol, more preferably 500,000-8,000,000 g / mol.

[0037] The net anionic copolymers of (meth)acrylamide may be linear or cross-linked and are prepared by any suitable polymerization method, such as solution polymerization, dispersion polymerization, emulsion or suspension polymerization, inverse emulsion polymerization, gel polymerization, or bead polymerization.

[0038] According to one embodiment, the anionic first polymer of the second component is a net anionic copolymer of (meth)acrylamide, which is prepared by gel polymerization, dispersion polymerization, emulsion or suspension polymerization, inverse emulsion polymerization, or bead polymerization, preferably by gel polymerization. The net anionic copolymer of (meth)acrylamide may have a weight average molecular weight (MW) of at least 1,500,000 g / mol, preferably at least 2,000,000 g / mol, and more preferably at least 3,000,000 g / mol. The weight average molecular weight (MW) may be in the range of 1,500,000 to 20,000,000 g / mol, preferably 2,000,000 to 15,000,000 g / mol, and more preferably 3,000,000 to 10,000,000 g / mol.

[0039] According to a preferred embodiment, the anionic first polymer of the second component is a net anionic copolymer of (meth)acrylamide prepared, for example, by solution polymerization of (meth)acrylamide and acrylic acid. The net anionic copolymer of (meth)acrylamide may have a weight average molecular weight (MW) of at least 200,000 g / mol, preferably at least 300,000 g / mol, and more preferably at least 500,000 g / mol. The weight average molecular weight (MW) may be in the range of 200,000-2,000,000 g / mol, preferably 300,000-1,500,000 g / mol, and more preferably 500,000-900,000 g / mol.

[0040] According to one embodiment of the present invention, the anionic first polymer of the second component can be obtained by polymerization of (meth)acrylamide and at least one anionic monomer, and can have an anionicity of 3-40 mol%, preferably 5-18 mol%, and more preferably 9-15 mol%. The anionicity is related to the amount of structural units in the anionic first polymer derived from the anionic monomer.

[0041] According to one embodiment of the present invention, the charge ratio of the cationic charge of the first component to the anionic charge of the second component is 4:1 to 1:1, which is provided as an absolute charge, at pH 7. The ratio of the first component to the second component is selected so that the chemical treatment system is net cationic at the pH of the fiber stock, i.e., when the pH of the fiber stock is in the range of 5.5-9, preferably 6.5-8.

[0042] The first component of the chemical treatment system may be added to the fiber stock in an amount of 0.5-5 kg / t, preferably 1-3 kg / t, and the second component of the chemical treatment system may be added to the fiber stock in an amount of 0.5-5 kg / t, preferably 1-3 kg / t.

[0043] The chemical treatment system according to the present invention is particularly suitable for fiber stockpiles containing recycled fibers and / or chemical pulp. The chemical treatment system is particularly suitable for fiber stockpiles consisting of recycled fibers. The chemical treatment system according to the present invention is particularly suitable for fiber stockpiles, preferably containing or consisting of recycled fibers. The fiber stockpiles may preferably have an electrical conductivity of at least 1 mS / cm, preferably at least 2 mS / cm, and sometimes even at least 4 mS / cm. The fiber stockpiles may have an electrical conductivity in the range of 1-6 mS / cm, preferably 2-5 mS / cm. DETAILED DESCRIPTION

[0044] experiment

[0045] Some embodiments of the invention are more closely described in the following non-limiting examples.

[0046] In the following examples, the criteria and apparatus used to evaluate board / paper performance are provided in Table 1.

[0047] Table 1 Paper sheet testing equipment and standard methods used in the examples

[0048] Measurement Device standard Basis weight Mettler Toledo ISO 536 Short-term compressive strength (SCT) Lorentzen & Wettre ISO 9895 Burst strength Lorentzen & Wettre ISO 2758 Corrugated Sandwich Medium Test (CMT30) Lorentzen & Wettre ISO 7263 Ring Compression Test (RCT) Lorentzen & Wettre Tappi T 822om-02

[0049] Example 1

[0050] Example 1 investigated the effect of a chemical treatment system on short term compressive strength (SCT), burst strength and crush strength as measured by the Corrugated Medium Test (CMT30).

[0051] The fiber stock of Example 1 was prepared from European recycled fiberboard (RCF).

[0052] The following chemical additives were used in Example 1:

[0053] GPAM: In-situ glyoxylated polyacrylamide, dry content 4.4 wt%. The base polymer was obtained by polymerization of 77 mol% acrylamide and 23 mol% diallyldimethylammonium chloride (DADMAC). The base polymer had a weight-average molecular weight (MW) of 123,000 g / mol, as determined by size exclusion chromatography calibrated with polyethylene oxide (PEO) standards. The base polymer had a number-average molecular weight (Mn) of 34,000 g / mol.

[0054] PEC1: polyelectrolyte complex comprising cationic waxy starch DS 0.07 (50% by weight of the complex) and anionic polyacrylamide (MW 593,000 g / mol, Mn 51,000 g / mol, 50% by weight of the complex) obtained by polymerization of 89 mol% acrylamide and 11 mol% acrylic acid. The polyelectrolyte complex has a pH of 6.5 and a charge density of 0.20 meq / g when measured at pH 2.8 and -0.55 meq / g when measured at pH 7.

[0055] PEC2: polyelectrolyte complex comprising cationic waxy starch DS 0.07 (58 wt% of the complex) and carboxymethylcellulose CMC, DS 0.7 (MW 450,000 g / mol, 42 wt% of the complex). The polyelectrolyte complex has a pH of 6.5 and a charge density of 0.23 meq / g when measured at pH 2.8 and a charge density of -1.1 meq / g when measured at pH 7.

[0056] The GPAM addition level is 3.5 kg / t and the addition level of PEC1 or PEC2 is 2.5 kg / t. Chemical addition levels are provided as kg dry chemical per tonne of dry fiber stock.

[0057] Handsheets were formed using a Rapid Koethen sheet former, 110 g / m 2 The procedure was as follows: RCF was wet-disintegrated (without soaking) at 70°C at a consistency of 3% using a Noviprofibre beater at 500 rpm for 30 seconds and 1000 rpm for 25 minutes. The resulting wet-disintegrated fiber stock was further diluted with tap water to a consistency of 0.6%, and the pH and conductivity of the fiber stock were adjusted to pH 6.8 and a conductivity of 4.0 mS / cm. Chemical additives were added to the mixing vessel at a stirring speed of 1000 rpm.

[0058] First, GPAM was added to the pulp 60 seconds before sheet formation, and then used PEC was added 40 seconds before sheet formation. All tests included the addition of cationic polyacrylamide, 100 g / t, and silica as a retention aid, 400 g / t.

[0059] After the chemical additives were added, the fiber stock was poured into a Rapid Koethen sheet former, and the water was drained through a wire mesh by suction. The resulting handsheets were removed from the mesh and dried in a vacuum dryer. Before laboratory testing, the handsheets were preconditioned at 23°C and 50% relative humidity for 24 hours according to ISO 187.

[0060] The resulting handsheets were tested for bursting strength, SCT strength, and crushing strength by using the standards and apparatus defined in Table 1.

[0061] The test results are provided in Table 2. From the results in Table 2, it can be seen that the chemical treatment system comprising GPAM as the first component and PEC1 or PEC2 as the second component significantly improved all strength properties compared to GPAM alone.

[0062] Table 2 shows the results of Example 1 showing the effect of different strength systems on paperboard properties.

[0063]

[0064]

[0065] Example 2

[0066] Example 2 investigated the effect of the chemical treatment system on burst strength and crush strength as measured by a Ring Compression Tester (RCT).

[0067] The fiber stock of Example 1 was prepared from old Chinese corrugated containerboard (OCC).

[0068] Handsheets were formed using a Rapid Koethen sheet former, 110 g / m 2 The procedure was as follows: RCF was wet-disintegrated (without soaking) at 70°C for 30,000 cycles at a consistency of 3% in a laboratory beater. The resulting wet-disintegrated fiber stock was further diluted with tap water to a consistency of 1%, and the pH and conductivity of the fiber stock were adjusted to pH 7 and a conductivity of 3.0 mS / cm. Chemical additives were added to the mixing vessel at a stirring speed of 1000 rpm.

[0069] The same chemical additives as in Example 1 were used in Example 2:

[0070] GPAM was added at an addition level of 1.5 kg / t or 2.5 kg / t and PEC1 or PEC2 was added at an addition level of 1 kg / t or 2 kg / t. Chemical addition levels are provided as kg dry chemical per tonne dry fiber stock.

[0071] First, GPAM was added to the pulp 60 seconds before sheet formation, and then used PEC was added 40 seconds before sheet formation. All tests included the addition of cationic polyacrylamide as a retention aid, 300 g / t.

[0072] After the chemical additives were added, the fiber stock was poured into a Rapid Koethen sheet former, and the water was drained through a wire mesh by suction. The resulting handsheets were removed from the mesh and dried in a vacuum dryer. Before laboratory testing, the handsheets were preconditioned at 23°C and 50% relative humidity for 24 hours according to ISO 187.

[0073] The resulting handsheets were tested for bursting strength and resistance to crushing (RTC) using the criteria and apparatus defined in Table 1.

[0074] The test results are provided in Table 3. From the results in Table 3, it can be seen that the chemical treatment system comprising GPAM as the first component and PEC1 or PEC2 as the second component significantly improved all strength properties compared to GPAM alone.

[0075] Even though the invention has been described with reference to what currently appear to be the most practical and preferred embodiments, it should be understood that the invention should not be restricted to the embodiments described above, but that the invention is intended to also cover different modifications and equivalent technical solutions within the scope of the appended claims.

[0076] Table 3 shows the results of Example 2 showing the effect of different strength systems on paperboard properties.

[0077]

[0078]

Claims

1. A chemical processing system for making paper, paperboard or the like, said processing system comprising - a first component, which is a glyoxylated polyacrylamide having a net cationic charge density and is obtained by glyoxylation by reacting a cationic polyacrylamide base polymer with 4 to 25 wt. % of glyoxal, the cationic polyacrylamide base polymer having a weight average molecular weight MW in the range of 30,000 to 500,000 g / mol, the amount of glyoxal being calculated on the total weight of the glyoxal and the polyacrylamide base polymer, and - A second component comprising a mixture of at least: - cationic non-degradable highly amylopectin starch, and - an anionic first polymer having a weight average molecular weight MW > 200000 g / mol, wherein the second component has a net cationic charge density in the range of 0.05 meq / g to 0.9 meq / g when measured at pH 2.8, and a net anionic charge density in the range of -2 meq / g to -0.1 meq / g when measured at pH 7.

2. The chemical treatment system according to claim 1, characterized in that The second component has a net anionic charge density in the range of -2 meq / g to -0.4 meq / g when measured at pH 7.

3. The chemical treatment system according to claim 1, characterized in that At pH 7, the charge ratio of the cationic charge of the first component to the anionic charge of the second component is from 4:1 to 1:

1.

4. A chemical treatment system according to claim 1, 2 or 3, characterized in that The high-branched starch is a cationic starch having a branched-chain starch content of ≥90 wt % based on the total dry weight of the starch.

5. A chemical treatment system according to claim 1, characterized in that The first polymer of the second component is selected from carboxymethyl cellulose or a net anionic copolymer selected from (meth)acrylamide.

6. The chemical treatment system according to claim 5, characterized in that The first polymer is a net anionic copolymer of (meth)acrylamide having a weight average molecular weight of at least 1,500,000 g / mol.

7. The chemical treatment system according to claim 5, characterized in that The first polymer is carboxymethyl cellulose having a weight average molecular weight of at least 200,000 g / mol.

8. The chemical treatment system according to claim 1, characterized in that The second component comprises high-branched starch in an amount of 20-80 wt%.

9. The chemical treatment system according to claim 1, characterized in that The cationic polyacrylamide base polymer of the first component has a weight average molecular weight in the range of 40,000-400,000 g / mol.

10. The chemical treatment system according to claim 1, characterized in that The cationic polyacrylamide base polymer of the first component is obtained by polymerization of acrylamide and at least one cationic monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), 3-(acrylamidopropyl)trimethylammonium chloride (APTAC) and 3-(methacrylamidopropyl)trimethylammonium chloride (MAPTAC).

11. The chemical treatment system according to claim 1, characterized in that The cationic polyacrylamide base polymer of the first component is obtained by polymerization of 10-50 mol % of cationic monomers.

12. The chemical treatment system according to claim 1, characterized in that The first component is a glyoxylated polyacrylamide obtained by reacting the cationic polyacrylamide base polymer with 8-15 wt % of the glyoxal, based on the total weight of glyoxal and the acrylamide base polymer.

13. Use of a chemical treatment system comprising the first component and the second component according to any one of claims 1 to 12 for improving the strength properties of paper or board by adding the chemical treatment system to a fiber stock.

14. The use according to claim 13, characterized in that The first component of the chemical treatment system is added to the fiber stock in an amount of 0.5-5 kg / t, and the second component of the chemical treatment system is added to the fiber stock in an amount of 0.5-5 kg / t.

15. The use according to claim 13 or 14, characterized in that The fiber stock comprises recycled fibers, and / or the fiber stock has an electrical conductivity of at least 2 mS / cm.

16. The use according to claim 13, characterized in that The first component and the second component of the chemical treatment system are added separately and continuously to the fiber stock.

17. A method for manufacturing paper or paperboard, the method comprising - obtaining a fiber stock comprising cellulose fibers, - adding a chemical treatment system according to any one of claims 1 to 12 to the fiber stock, the chemical treatment system comprising a first component and a second component, wherein the first component and the second component are added to the fiber stock in the form of aqueous solutions.

18. The method according to claim 17, characterized in that Prior to adding the second component to the fiber stock, the second component is formed by mixing the highly amylopectin starch and the first polymer with one another.

19. The method according to claim 17 or 18, characterized in that The first component and the second component are added to the fiber stock having a consistency of at least 2% by weight based on dry fiber.

20. The method according to claim 17, characterized in that The first component is obtained by in situ glyoxylation of an aqueous base polymer composition.

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