Starch composition, method of manufacturing the same, and paper-making strength agent comrising the same

Abstract

Embodiments of the present invention provide a starch composition comprising a cationic starch; and a cationic polymer, wherein the cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the weight average molecular weight of the cationic polymer measured by GPC is 2,000,000 g / mol or less.

Description

Technology Field

[0001] The present invention relates to a starch composition, a method for preparing the same, and a strength enhancer for papermaking comprising the same. More specifically, the invention relates to a starch composition comprising cationic starch and polyacrylamide, a method for preparing the same, and a strength enhancer for papermaking comprising the same. Background Technology

[0003] In order to manufacture paper, cardboard, tissue, etc., a source such as wood or fiber can be pulped, and an aqueous slurry containing cellulose fibers can be obtained from the pulp. The aqueous slurry can be converted into a final product such as paper through processing steps such as drainage, drying, and pressing.

[0004] Various additives are used during the above papermaking process to improve the quality of the final product, and, for example, these additives can be used to improve the strength, retention rate, density, etc. of the final product.

[0005] Starch may be used as one of the aforementioned additives. Starch can function as an enhancer and can be added to the papermaking process to improve the tensile strength of the final product. For example, cationic starch can be absorbed into fibers to develop hydrogen bonds between them, thereby binding the fibers strongly together and increasing the strength of the final product.

[0006] Meanwhile, for starch to be introduced into the papermaking process, it is required to be dissolved in water. Accordingly, a cooking process for the starch may be performed to dissolve the starch in water. For example, a starch solution can be obtained by cooking an aqueous starch slurry containing water and starch using a jet cooker.

[0007] However, as the cooking process is carried out under harsh conditions of high temperature and pressure, glycosidic bonds within the starch may be broken or the starch may be fragmented due to hydrolysis or thermal decomposition during the cooking process. For example, at the beginning of the cooking process, the starch may swell and dissolve in water, increasing viscosity, but then individual starch molecules may desorb and the starch may decompose, causing the viscosity to decrease again. If the molecular weight or viscosity of the starch decreases, the charge of the starch may be lowered or the interaction between the starch and the fiber may be reduced, resulting in poor adsorption of the starch onto the fiber surface. Furthermore, if the molecular weight of the starch decreases, some of the starch may be buried within defect areas on the fiber surface, preventing the starch from performing its intended function. In this case, the improvement effect on the strength and retention rate of the final product may be reduced, and linting and dusting of the paper may occur.

[0008] Therefore, research is required on a technology that can improve the quality of the final product by replenishing the molecular weight and viscosity of starch lost during the cooking process and promoting efficient interaction between the starch and the final product. The problem to be solved

[0010] The present invention relates to a starch composition capable of improving the quality of paper products, a method for manufacturing the same, and a paper strength enhancer comprising the same. means of solving the problem

[0012] According to embodiments of the present invention, a starch composition is provided comprising a cationic starch; and a cationic polymer, wherein the cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the weight average molecular weight of the cationic polymer measured by GPC is 2,000,000 g / mol or less.

[0013] According to embodiments of the present invention, a method for preparing a starch composition is provided, comprising the steps of: cooking a starch mixture to obtain a cationic starch slurry; and adding a cationic polymer solution to the cationic starch slurry, wherein the cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the weight average molecular weight of the cationic polymer is 2,000,000 g / mol or less.

[0014] According to embodiments of the present invention, a paper strength enhancer comprising a starch composition according to the above embodiments is provided. Effects of the invention

[0016] According to embodiments of the present invention, a starch composition comprises a cationic copolymer having a branched structure together with cationic starch, wherein the cationic copolymer comprises cationic monomers having a weight-average molecular weight within a predetermined range and a predetermined content. Accordingly, the cationic copolymer can form a complex with the cationic starch or act as a linker between cationic starch molecules to restore the molecular weight and viscosity of the cationic starch that have decreased during the cooking process.

[0017] When the above starch composition is introduced into a papermaking process, for example, into fiber furnish or fiber stock, the interaction between the cationic starch and the fibers is further enhanced, which can increase the bonding strength between the fibers and improve the quality of the final product, such as strength, retention rate, and density. Brief explanation of the drawing

[0019] Figure 1 is a schematic diagram illustrating the interaction between cationic starch and cationic polymer. Figure 2 is a schematic diagram illustrating the interaction according to the ion distribution of an amphoteric polymer. FIG. 3 is a schematic diagram illustrating a manufacturing facility for a starch composition according to one embodiment of the present invention. Figures 4a and 4b are photographic images of a solution of the amphoteric polymer diluted in Experimental Example 5, respectively. Specific details for implementing the invention

[0020] Hereinafter, embodiments are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the above embodiments may be implemented in various different forms, and the present invention is not limited to the embodiments described herein. Furthermore, the sizes of each component in the drawings may be exaggerated or omitted for illustrative purposes and may differ from the actual sizes applied.

[0021] In describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0022] In this specification, when a part is described as "comprising" a certain component, this is intended to specify a particular characteristic, area, step, process, element, and / or component, and unless specifically stated otherwise, it does not exclude the presence or addition of other characteristics, areas, steps, processes, elements, and / or components.

[0023] In this specification, the description that one component is formed above or below another component, or is connected or coupled to one another, includes both direct formation, connection, or coupling between these components and indirect formation, connection, or coupling through the interposition of another component. Additionally, the reference for the above and below of each component may vary depending on the direction in which the object is observed.

[0024] In this specification, singular expressions are interpreted to include singular or plural forms as interpreted in context unless otherwise specified.

[0025] In addition, all numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term "about" in all cases unless otherwise specified.

[0026] In this specification, terms such as "first," "second," etc. are used to describe various components, and said components are not to be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0028] <Starch Composition>

[0029] A starch composition according to embodiments of the present invention comprises cationic starch and a cationic polymer.

[0030] The cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, wherein the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the relative weight average molecular weight of the cationic polymer may be 2,000,000 g / mol or less.

[0031] The above cationic starch includes natural starch having cationic groups, or starch modified to have cationic groups.

[0032] The above starch may include amylopectin and amylose. The amylopectin and amylose are each natural polymers containing glucose units.

[0033] The amylose has a linear structure and may have a relatively small number of glucose units and a small molecular weight. For example, the amylose may have a linear bonding structure through an α-1,4-bond connecting the 1st and 4th carbons of alpha-glucose. The amylopectin has a branched structure and may have a relatively large number of glucose units and a large molecular weight. For example, the amylopectin may have a structure with multiple branches formed, including an α-1,6-bond connecting the 1st and 6th carbons of glucose.

[0034] In one embodiment, the amylopectin content of the starch component may be 60% to 99.9% by weight, 70% to 90% by weight, or 75% to 85% by weight based on the total weight of the starch. In one embodiment, the amylose content of the starch component may be 0.1% to 40% by weight, 10% to 30% by weight, or 15% to 25% by weight based on the total weight of the starch. In this case, the content of small-sized amylose is limited, thereby increasing the interaction between the starch and the fiber while also improving the efficiency of the process cost.

[0035] The above starch may include, but is not limited to, potato starch, waxy potato starch, rice starch, corn starch, waxy maize starch, wheat starch, barley starch, tapioca starch, sweet potato starch, sago starch, cassava starch, or a combination thereof. In one embodiment, the starch may include potato starch, rice starch, corn starch, waxy maize starch, wheat starch, or tapioca starch.

[0036] The above starch can be cationized by known methods. For example, the above starch can be cationized using a protonating agent. The above protonating agent refers to a compound having a reactive group at one end capable of binding to the hydroxyl group of the starch and a cationic group at the other end. Examples of the above protonating agents include diethylaminoethyl chloride, 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxytrimethylammonium chloride, glycidyltrimethylammonium chloride, etc.

[0037] In one embodiment, the starch may be cationized using a cationic acrylamide derivative such as (3-acrylamidopropyl)-trimethylammonium chloride.

[0038] As the above starch composition includes cationic starch, interaction with the surface of anionic fibers can be enhanced, which improves starch retention and drainage in the fibers and improves strength characteristics such as tensile strength and burst strength of the final produced paper.

[0039] The cationic starch can be obtained by cooking a starch mixture. The starch mixture comprises starch and water. The cooking involves heating the starch mixture at a temperature above the gelatinization temperature. Accordingly, the starch in the starch mixture dissolves in water to obtain a cationic starch slurry. For example, the cationic starch slurry may be an aqueous solution of cooked cationic starch.

[0040] In one embodiment, the cooking may be performed after the cationization of the starch, or may be performed together with the cationization of the starch.

[0041] The above cooking can be performed using a batch cooker or a continuous cooker. In one embodiment, the cooking can be performed using a batch cooker. Alternatively, the cooking may be performed by a continuous cooker such as a jet cooker, in which case the starch can be cooked continuously at a faster speed, reducing process costs and improving productivity.

[0042] Meanwhile, the molecular weight of the cationic starch may decrease during the cooking process. For example, the cationic starch may be fragmented as glycoside bonds within the starch molecular structure are broken by thermal decomposition or hydrolysis during the cooking process. In this case, the reactivity of the cationic starch may decrease, thereby reducing its interaction with the fiber, or the cationic starch may be buried in defect areas on the fiber surface, reducing the intended role of the starch, which may result in a problem requiring a larger amount of starch.

[0043] In one embodiment, the cationic starch may have a relatively low viscosity as the molecular weight decreases due to decomposition of the cationic starch by cooking. For example, the cationic starch may have a viscosity of 20 cps to 100 cps when measured in an aqueous solution containing 1 weight% of cationic starch using a Brookfield viscometer at 50°C.

[0044] The above-mentioned cationic starch is required to have a high molecular weight and viscosity when introduced into the papermaking process. For example, the higher the molecular weight of the cationic starch, the better the starch retention in the fibers can be, and the greater the enhancement of paper strength by the starch can be. The molecular weight of the cationic starch may have a positive correlation with viscosity; for example, as the molecular weight of the cationic starch increases, the viscosity of the starch composition may increase.

[0045] By including the cationic polymer together with the cationic starch in the above starch composition, the molecular weight of the cationic starch is restored, and viscosity may increase. In addition, due to the synergy between the cationic starch and the cationic polymer, starch retention in the fiber may be improved, and the strength and drainage characteristics of the produced paper and / or paper product may be improved.

[0046] Specifically, the viscosity of the starch composition may be 100 cps or more when measured using a Brookfield viscometer at 50°C, for example, 100 cps to 250 cps, 120 cps to 250 cps, or 120 cps to 200 cps.

[0047] In one embodiment, the viscosity of the cationic polymer may be 50 to 90 cps when measured in an aqueous solution containing 1 weight% of the cationic polymer using a Brookfield viscometer at 50°C.

[0048] In one embodiment, the viscosity of the starch composition may be greater than the sum of the viscosity of the cationic starch slurry and the viscosity of the cationic polymer solution. As the cationic starch and the cationic polymer combine to form a complex, the molecular weight and viscosity may be further enhanced.

[0049] For example, referring to FIG. 1, the cationic polymer may have a reactive group capable of binding to the hydroxyl group of cationic starch (C-starch). For example, the cationic polymer may have a reactive group capable of binding to the hydroxyl group of the starch at one end of the backbone and a cationic group at the other end. Accordingly, the cationic starch and the cationic polymer can form a polyelectrolyte complex (PEC) within the starch composition.

[0050] By forming the polymer electrolyte complex by including the cationic polymer together with the cationic starch in the above starch composition, the reactivity and molecular weight of the cationic starch can be increased, and the cationic starch can be more efficiently maintained and fixed to the fiber.

[0051] The above cationic polymer may include a copolymer of a monomer blend comprising a nonionic monomer and a cationic monomer. The above nonionic monomer generally refers to a monomer having a neutral charge, and the above cationic monomer generally refers to a monomer having a positive charge.

[0052] The above cationic polymer may be an inverse emulsion (water-in-oil) polymer. For example, the cationic polymer can be obtained by inverse emulsion polymerizing the above monomer blend.

[0053] The above monomer blend may include a cationic monomer, thereby obtaining a copolymer having cationic properties.

[0054] The above nonionic monomer may include an acrylamide-based monomer. Specifically, the above cationic polymer may be a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer. For example, the above cationic polymer may include cationic polyacrylamide.

[0055] The above acrylamide-based monomer may include (meth)acrylamide; N-alkyl acrylamides such as N-methylacrylamide; N,N-dialkylacrylamides such as N,N-dimethylacrylamide; etc. These may be included alone or in combination of two or more.

[0056] The above cationic monomers may include diallyldimethylammonium chloride (DADMAC); acryloyloxyethyltrimethylammonium chloride; N,N-dialkylaminoalkyl (meth)acrylate, its tetroxide and salt (e.g., N,N-dimethylaminoethylacrylate methyl-chloride salt); N,N-dialkylaminoalkyl (meth)acrylamide, its salt and tetroxide (e.g., N,N-dialkylaminoethylacrylamide); methacrylamidopropyltrimethylammonium chloride; 1-methacryloyl-4-methylpiperazine, etc. These may be included alone or in combination of two or more.

[0057] The content of the cationic monomer may be 15 mol% to 50 mol% of the monomer blend. For example, the content of the cationic monomer may be 15 mol% to 40 mol%, 20 mol% to 40 mol%, or 20 mol% to 30 mol% of the monomer blend.

[0058] The cationic polymer comprises structural units having cationic groups, and the structural units having cationic groups may be derived from the cationic monomer. For example, the cationic polymer may comprise structural units having cationic groups in an amount of 15 mol% to 50 mol%, 15 mol% to 40 mol%, 20 mol% to 40 mol%, or 20 mol% to 30 mol%.

[0059] Within the above range, the cationic polymer can have an appropriate range of cationic charge, thereby enhancing reactivity with cationic starch while improving the fixation efficiency of cationic starch on the fiber.

[0060] The weight-average molecular weight (Mw) of the above cationic polymer is 2,000,000 g / mol or less. The weight-average molecular weight of the above cationic polymer can be measured by gel permeation chromatography (GPC). The molecular weight calculation by GPC can be performed using polyethylene oxide as a standard material.

[0061] As the cationic polymer has a low weight-average molecular weight, it can increase the enhancement effect of the starch through interaction with the cationic starch. For example, if the cationic polymer has a low molecular weight (e.g., 2,000,000 g / mol or less), it can suppress the phenomenon of fibers over-flocculating due to high molecular weight polymers, and accordingly, the strength and quality of the paper can be improved.

[0062] In one embodiment, the weight average molecular weight of the cationic polymer may be 1,800,000 g / mol or less, 1,600,000 g / mol or less, 1,400,000 g / mol or less, or 1,200,000 g / mol or less. For example, the weight average molecular weight of the cationic polymer may be 800,000 g / mol to 2,000,000 g / mol, 800,000 g / mol to 1,800,000 g / mol, 800,000 g / mol to 1,600,000 g / mol, 800,000 g / mol to 1,400,000 g / mol, or 800,000 g / mol to 1,200,000 g / mol.

[0063] The above cationic polymer has a branched structure. By having a branched structure, the reactivity to the cationic starch is further enhanced, and the cationic polymer and the cationic starch can form a complex having a larger size and molecular weight. Accordingly, the interaction between the cationic starch and the fiber is further enhanced, improving the adsorption, retention, and drainage of starch on the fiber, and consequently, the bonding strength between fibers is enhanced, which can improve the quality of the paper.

[0064] A branched copolymer can be obtained by using a chain transfer agent and a crosslinking agent during the polymerization of the above monomer blend. The degree of branching of the cationic polymer can be controlled to a desired range by adjusting the concentrations of the chain transfer agent and the crosslinking agent. For example, a crosslinking agent may be added to the monomer blend at a concentration of 50 ppm or less, 5 ppm to 30 ppm, or 10 ppm to 20 ppm. Additionally, the chain transfer agent may be added to the monomer blend at a concentration of 300 ppm to 500 ppm.

[0065] The above chain transfer agent may include alcohols; mercaptans; thio acids; phosphites and sulfites, etc., and may include, for example, isopropyl alcohol or sodium hypophosphite, but is not limited thereto.

[0066] The above crosslinking agent may include, but is not limited to, methylenebisacrylamide; methylenebismethacrylamide; polyethylene glycol diacrylate; polyethylene glycol dimethacrylate; N-vinyl acrylamide; divinylbenzene; trialylammonium salt; N-methylallylacrylamide; glycidyl acrylate; acrolein; methylolacrylamide; aldehydes such as glyoxal; diepoxy compounds; epichlorohydrin, etc.

[0067] In one embodiment, the degree of branching of the cationic polymer represented by the following formula 1 may be 100 to 200.

[0068] [Equation 1]

[0069] Degree of Branching = Bulk Viscosity / Standard Viscosity

[0070] The above bulk viscosity is the viscosity at 25°C of a reverse-phase emulsion solution containing 0.2 wt% of a cationic polymer, and the above standard viscosity is the viscosity at 25°C of a 1 M NaCl solution containing 0.1 wt% of a cationic polymer. The above bulk viscosity and standard viscosity can be measured using a Brookfield viscometer.

[0071] The above reverse phase emulsion solution comprises an emulsion of a cationic polymer that is completely inverted into an aqueous solution. For example, the above reverse phase emulsion solution may be a cationic polymer solution described below.

[0072] By having a degree of branching of 100 to 200, the above cationic polymer can promote the increase in starch size and further enhance the reactivity of starch and fiber, thereby further improving the strength, retention, and drainage properties of the paper by the starch.

[0073] In one embodiment, the content of the cationic polymer in the starch composition may be 0.5 to 4.0 parts by weight per 1 part by weight of the cationic starch. For example, the content of the cationic polymer in the starch composition may be 0.8 to 3.0 parts by weight, 1.0 to 2.5 parts by weight, 1.0 to 2.0 parts by weight, or 1.2 to 1.8 parts by weight per 1 part by weight of the cationic starch. Within the above ranges, the cationic polymer and cationic starch are included in an optimal range, thereby further enhancing the interaction between the cationic starch and the fibers, and further improving the internal bonding between the fibers. Additionally, physical properties such as tensile strength, burst strength, and stiffness of the paper may be further improved.

[0074] The above starch composition may further include an amphoteric polymer. For example, the above starch composition may include cationic starch, a cationic polymer, and an amphoteric polymer.

[0075] The above-mentioned amphoteric polymer refers to a polymer having both cation groups and anion groups. More specifically, the above-mentioned amphoteric polymer may have both cation groups and anion groups under conditions of pH 7. The cation and anion groups may be attached to the backbone of the copolymer.

[0076] The anionic group of the above-mentioned amphoteric polymer can interact with cationic starch or a cationic starch-cationic polymer complex to form a larger cationic starch-amphoteric polymer complex or a cationic starch-cationic polymer-amphoteric polymer complex. Additionally, the cationic group of the above-mentioned amphoteric polymer can further improve the interaction between the fiber and the complex. Thus, the retention of starch in the fiber can be further enhanced, and the mechanical properties of the final product, such as strength, elongation, and break resistance, can be further improved.

[0077] The above-mentioned amphoteric polymer may include polyacrylamide. For example, the above-mentioned amphoteric polymer may include a structural unit derived from an acrylamide-based monomer, a structural unit including an anionic group, and a structural unit including a cation group.

[0078] In one embodiment, the structural unit containing the anionic group may be derived from an anionic monomer. Additionally, the structural unit containing the cation may be derived from a cationic monomer. For example, the amphoteric polymer may be a copolymer of a monomer blend comprising an acrylamide monomer, an anionic monomer, and a cationic monomer.

[0079] As the acrylamide-based monomer and the cationic monomer, monomers described in the cationic polymer may be used, but are not limited thereto.

[0080] The above anionic monomer may include, but is not limited to, (meth)acrylic acid, maleic acid, crotonic acid, itaconic acid, vinylsulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylphosphonic acid, or ethylene glycol methacrylate phosphate.

[0081] In one embodiment, the content of cation groups in the amphoteric polymer may be greater than the content of anion groups. The content of cationic monomers in the monomer blend of the amphoteric polymer may be higher than the content of anionic monomers. Accordingly, the net charge of the starch composition may have a positive value.

[0082] For example, the content of the cationic monomer in the monomer blend may be 5 mol% to 30 mol%, 10 mol% to 30 mol%, or 10 mol% to 20 mol%, and the content of the anionic monomer may be 1 mol% to 10 mol%, 2 mol% to 8 mol%, or 2 mol% to 5 mol%.

[0083] The above-mentioned amphoteric polymer may have a smaller molecular weight than the above-mentioned cationic polymer.

[0084] In one embodiment, the weight-average molecular weight of the amphoteric polymer measured by the GPC method may be 1,000,000 g / mol or less. For example, the weight-average molecular weight of the amphoteric polymer measured by the GPC method may be 100,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 1,000,000 g / mol, 200,000 g / mol to 900,000 g / mol, 200,000 g / mol to 800,000 g / mol, or 300,000 g / mol to 700,000 g / mol.

[0085] The molecular weight measured by the above GPC method may represent a relative molecular weight. Polyethylene oxide may be used as a standard material when calculating the molecular weight using the above GPC method.

[0086] In one embodiment, the weight-average molecular weight of the amphoteric polymer measured by the GPC-LS method may be 3,000,000 g / mol to 5,000,000 g / mol. For example, the weight-average molecular weight of the amphoteric polymer measured by the GPC-LS method may be 3,000,000 g / mol to 4,500,000 g / mol, 3,500,000 g / mol to 4,500,000 g / mol, or 3,500,000 g / mol to 4,000,000 g / mol.

[0087] The molecular weight measured by the above GPC-LS method refers to the absolute molecular weight and can be measured using gel permeation chromatography (GPC) and a light scattering (LS) detector. A multi-angle light scattering (MALS) detector can be used as the light scattering detector.

[0088] Within the above molecular weight range, the reactivity between cationic starch and fibers can be further enhanced. Accordingly, the bonding strength between fibers, the tensile strength and breaking strength of the paper, etc., can be further improved.

[0089] In one embodiment, the cation group and the anion group of the amphoteric polymer may each be located in a local region within the molecular structure. For example, one end of the amphoteric polymer may have a local cationic charge, and the other end may have a local anionic charge.

[0090] For example, referring to (A) of FIG. 2, when the amphoteric polymer has a localized ion distribution, it can easily interact with other amphoteric polymers, cationic polymers, and / or cationic starches within the composition to form a poly-ion complex or polymer electrolyte complex (PEC) of a larger volume, which can facilitate adsorption onto the fiber. Additionally, since the adsorption of the polymer onto the fiber depends more heavily on the cationic charge group, the adsorption of the complex onto the fiber can be further enhanced due to the cation distribution at the terminal end of the amphoteric polymer.

[0091] On the other hand, referring to (B) of FIG. 2, when the cation and anion groups of the amphoteric polymer are randomly distributed within the molecular structure, it may be relatively difficult to form a composite because the amphoteric polymer is uniformly dispersed within the composition due to the charge stabilization effect. In addition, as the interaction due to the cationic charge is relatively weak, the effect of improving adsorption to the fiber may not be relatively large.

[0092] In one embodiment, the content of the amphoteric polymer in the starch composition may be 0.1 to 2 parts by weight per 1 part by weight of the cationic starch. For example, the content of the amphoteric polymer in the starch composition may be 0.1 to 1.8 parts by weight, 0.1 to 1.2 parts by weight, 0.1 to 0.5 parts by weight, or 0.1 to 0.3 parts by weight per 1 part by weight of the cationic starch. Within the above range, the molecular weight and viscosity of the cooked cationic starch may be further increased, and the starch's retention power on the fiber may be enhanced, thereby further improving the quality of the paper.

[0093] In one embodiment, the starch composition may further include known additives within a range that does not impede the effects of the present invention. For example, the additives may further include cationic coagulants, anionic coagulants, enhancers, maintenance aids, drainage aids, fillers, stabilizers, etc.

[0095] Method for preparing a starch composition

[0096] According to one embodiment of the present invention, a method for preparing a starch composition is provided, comprising the steps of: cooking a starch mixture containing cationic starch and water to obtain a cationic starch slurry (e.g., step S10); and adding a cationic polymer solution to the cationic starch slurry (e.g., step S20).

[0097] The cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, wherein the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the molecular weight of the cationic polymer may be 2,000,000 g / mol or less.

[0098] In the above S10 step, a cationic starch slurry can be obtained by cooking a starch mixture containing cationic starch and water.

[0099] The above cationic starch comprises a cationic starch component. The starch component may include, but is not limited to, potato starch, waxy potato starch, rice starch, corn starch, waxy maize starch, wheat starch, barley starch, tapioca starch, sweet potato starch, sago starch, cassava starch, or a combination thereof. The starch component may be cationicized by a known method.

[0100] The above cationic starch can be mixed with water to obtain a starch mixture. The above starch mixture can be cooked at a predetermined temperature.

[0101] In one embodiment, the cooking may be performed after the cationization of the starch. In another embodiment, the cooking may be performed together with the cationization of the starch.

[0102] The above cooking can be performed using a batch cooker or a continuous cooker, and, for example, can be performed using a method such as a jet cooker.

[0103] The temperature of the above cooking process may be higher than the gelatinization temperature of the cationic starch. Accordingly, the cationic starch in the starch mixture may be dissolved in water to obtain a cationic starch slurry. The cationic starch slurry may be an aqueous solution of cooked cationic starch.

[0104] In one embodiment, the cooking temperature for the starch mixture may be 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 120°C or higher, or 130°C or higher, and may be 150°C or lower. For example, the cooking temperature may be 70°C to 150°C, 80°C to 150°C, 90°C to 150°C, 100°C to 150°C, 120°C to 150°C, or 130°C to 150°C.

[0105] Within the above range, the cationic starch can be gelatinized more efficiently, and cooking time can be reduced, thereby further improving processability. In addition, even if the cationic starch is fragmented by cooking at the high temperature described above, the molecular weight, viscosity, and reactivity of the cationic starch can be restored by adding the cationic polymer described later.

[0106] In the above S20 step, a cationic polymer solution can be added to the cationic starch slurry to obtain a starch composition.

[0107] The above cationic polymer solution may be an inverse emulsion solution.

[0108] The above cationic polymer can be obtained by emulsion polymerization. In one embodiment, the cationic polymer can be prepared by reverse-phase emulsion polymerization, and the reverse-phase emulsion of the obtained cationic polymer can be inverted into an aqueous solution.

[0109] The above reverse-phase emulsion is a water-in-oil emulsion, and two phases may be prepared during the polymerization process of the reverse-phase emulsion. Specifically, a water phase may be prepared comprising a monomer, a crosslinking agent, and a chain transfer agent dissolved in water (e.g., deionized water), or further comprising additives as needed, and an oil phase comprising a water-insoluble hydrocarbon solution of a surfactant. The water phase and the oil phase may be mixed and homogenized until an emulsion having a suitable bulk viscosity is obtained. After shaking and purging the emulsion with nitrogen, a polymerization initiator may be added to the emulsion to initiate polymerization, and a polymerized emulsion polymer may be obtained.

[0110] Meanwhile, as the molecular weight of the polymer increases, dissolving the polymer may become difficult, and if the polymer is incompletely dissolved in the solution, the interaction of the polymer with starch or fiber may be reduced. According to embodiments of the present invention, the cationic polymer may exhibit high inversion and dissolution rates. Specifically, the emulsion inversion rate in water may increase as the cationic polymer has low viscosity resulting from a relatively low molecular weight, high cationic charge due to a high molar ratio of cationic monomers, and high branching. Therefore, the cationic polymer can be used immediately without aging and can be easily applied to the process using simple methods, such as a pump-and-go method.

[0111] For example, the cationic polymer solution may have a viscosity of 50 to 90 cps at a cationic polymer concentration of 1 wt%. The viscosity may be measured using a Brookfield viscometer equipped with a UL adapter at 50°C.

[0112] The solid content concentration (i.e., polymer concentration) of the above cationic polymer solution may be 0.1 wt% to 1.0 wt%. Within this range, the inversion and dissolution rates may be further increased, and the process may be applied more simply.

[0113] The above cationic polymer can form a polymer electrolyte complex with the cationic starch within the starch composition. The molecular weight and viscosity of the cationic starch can be restored by the cationic polymer.

[0114] In one embodiment, the viscosity of the starch composition at 50°C may be 2 to 5 times the viscosity of the cationic starch slurry at 50°C. For example, the viscosity of the starch composition may be 2 to 4.5 times, 2.5 to 4.5 times, or 3 to 4 times the viscosity of the cationic starch slurry.

[0115] By the above cationic polymer interacting with cationic starch to form a larger-sized complex, the viscosity of the starch composition can be significantly increased compared to the viscosity of the cationic starch slurry.

[0116] In one embodiment, the method for preparing the starch composition may further include the step of adding an amphoteric polymer solution to the cationic starch slurry (e.g., step S30).

[0117] In one embodiment, the solid content concentration (i.e., polymer concentration) of the amphoteric polymer solution may be 15% to 30% by weight, or 19% to 21% by weight. If the solid content concentration of the amphoteric polymer solution becomes excessively high, the viscosity increases excessively, which limits the increase in molecular weight and may reduce workability and productivity.

[0118] In one embodiment, the pH of the amphoteric polymer solution at 25°C may be 2.5 to 3.5. If the pH of the amphoteric polymer solution becomes excessively high, the cationic monomer may be hydrolyzed and lose its cationic properties.

[0119] In one embodiment, the viscosity of the amphoteric polymer solution may be 6,000 cps to 12,000 cps at 25°C. The viscosity may be measured using a Brookfield viscometer equipped with a UL adapter at 25°C.

[0120] In one embodiment, the amphoteric polymer solution may be introduced into the cationic starch slurry together with the cationic polymer solution, or the cationic polymer solution and the amphoteric polymer solution may be introduced sequentially into the cationic starch slurry.

[0122] <Starch Composition Manufacturing Equipment>

[0123] FIG. 3 is a schematic diagram illustrating a manufacturing facility for a starch composition according to one embodiment of the present invention.

[0124] A manufacturing facility for a starch composition according to one embodiment includes: a storage container (10) containing a starch component; a mixing tank (20) for mixing the starch component and water; a cooking stage (30) for cooking the mixture of the starch component and water; and a supply tank (40) for supplying a cationic polymer to the cooked starch slurry.

[0125] Starch components can be supplied from the storage container (10) to the mixing tank (20). Water (H2O) can be supplied to the mixing tank (20) through a different path from the storage container (10).

[0126] Starch components and water can be mixed in a mixing tank (20) to form a starch mixture.

[0127] The above starch mixture can be supplied from the mixing tank (20) to the cooking stage (30). In the cooking stage (30), steam can be injected to gelatinize the cationic starch. For example, the cooking stage (30) may include a steam injection unit (35).

[0128] The cooking stage (30) may have a batch or continuous structure. In one embodiment, the cooking stage (30) may have a continuous structure and may be, for example, a jet cooker.

[0129] The above starch mixture can be cooked in a cooking stage (30) to obtain a cationic starch slurry. The cationic starch slurry can be transported to a storage tank (50).

[0130] The above cationic polymer may be added during or after the cooking stage (30).

[0131] For example, before the cationic starch slurry is transported to the storage tank (50), or a cationic polymer solution may be supplied through the supply tank (40) into the storage tank (50).

[0132] In one embodiment, an amphoteric polymer solution may be further added to the cationic starch slurry. The amphoteric polymer solution may be added directly to the storage tank (50), or may be added to the cationic starch slurry before the cationic starch slurry is transported to the storage tank (50).

[0133] The starch composition stored in the storage tank (50) can be introduced into a papermaking process. For example, the starch composition can be supplied to fiber furnish or stock.

[0135] Paper Strength Enhancer

[0136] According to one embodiment of the present invention, a paper strength enhancer comprising the starch composition described above is provided.

[0137] The above paper strength enhancer can be added to the fiber furnish or stock before forming the fiber web.

[0138] The cationic starch or complex contained in the above starch composition can effectively interact with the negatively charged fiber surface within the furnish or stock, thereby increasing the bonding strength between fibers. Additionally, the retention and drainage properties of the starch on the fibers can be improved, and properties such as strength, elongation, and stiffness of the final produced paper can be enhanced.

[0139] According to one embodiment, a method for manufacturing paper or cardboard using the paper strength enhancer is provided.

[0140] The method for manufacturing the paper or cardboard comprises the steps of: preparing a fiber stock; adding a starch composition according to the embodiments described above to the fiber stock; and forming a fiber web from the fiber stock.

[0141] The fiber stock may include cellulose fibers. The fiber stock may be an aqueous suspension containing cellulose fibers. For example, the fiber stock may include a thin stock, a thick stock, a furnish, a pulp slurry, etc.

[0142] The paper strength enhancer can be added to the above aqueous suspension.

[0143] In one embodiment, the paper strength enhancer may be added such that the cationic starch is 0.5 to 2.0 parts by weight per 100 parts by weight of pulp contained in the aqueous suspension.

[0144] In one embodiment, the amount of the cationic polymer added may be 0.5 to 4.0 parts by weight, 0.8 to 3.0 parts by weight, 1.0 to 2.5 parts by weight, 1.0 to 2.0 parts by weight, or 1.2 to 1.8 parts by weight per 1 part by weight of the cationic starch.

[0145] In one embodiment, the amount of the amphoteric polymer added may be 0.1 to 2 parts by weight, 0.1 to 1.8 parts by weight, 0.1 to 1.2 parts by weight, 0.1 to 0.5 parts by weight, or 0.1 to 0.3 parts by weight per 1 part by weight of the cationic starch.

[0146] The above aqueous suspension can be transferred to a head box and drained to form a fiber web. The fiber web can be compressed and dried to obtain a web of paper or cardboard.

[0148] The above contents will be explained in more detail by the following examples. However, the following examples are merely for illustrating the present invention, and the scope of the present invention is not limited thereto.

[0150] <Preparation Example>

[0151] Preparation of cationic starch slurry A

[0152] Corn cationic starch (degree of substitution (DS): 0.02 to 0.06) was used as the cationic starch. The cationic starch was mixed with water in a predetermined amount to prepare a starch mixture, and the starch mixture was cooked in a batch at a temperature of 100°C at atmospheric pressure for 10 minutes to prepare a cationic starch slurry.

[0153] Preparation of cationic starch slurry B

[0154] Corn cationic starch (DS: 0.02 to 0.06) was used as the cationic starch. The cationic starch was mixed with water in a predetermined amount to prepare a starch mixture, and the starch mixture was cooked at 130°C at atmospheric pressure using a jet cooker to prepare cationic starch slurry B.

[0155] Preparation of cationic polymer solution

[0156] Polyacrylamide emulsion in water was synthesized through an inverse emulsion polymerization process. Acrylamide was used as the acrylamide-based monomer, acryloyloxyethyltrimethylammonium chloride as the cationic monomer, and methylene bis-acrylamide as the crosslinking agent.

[0157] Specifically, 231 g of acrylamide, 180 g of acryloyloxyethyltrimethylammonium chloride (30 mol% of the monomer blend), 34.30 g of citric acid, 2.1 g of isopropyl alcohol, and 58.5 g of water were added to a tared 1000 mL beaker (containing a magnetic stirring bar), and methylene bisacrylamide was added at 28 ppm of the total monomer to prepare an aqueous monomer blend. The pH of the monomer blend was adjusted to a range of 6.0 to 6.5 using ammonium hydroxide, and the temperature of the monomer blend was maintained below 30°C.

[0158] 154.1 g of Shellsol D-80 (paraffin solvent), 12.54 g of SMO (Arlacel 80AC), and 8.45 g of Tergitol L24-7 were added to a 1 L steel jug and stirred at 450 rpm for more than 10 minutes using an overhead mixer to prepare the oil phase.

[0159] The aqueous phase was added to the oil phase and mixed for about 20 minutes, and homogenized at 4500 rpm using a Ross homogenizer. Afterwards, the mixture was introduced into a polymerization reactor, 0.23 g of tert-butyl hydroperoxide (Trigonox A-W70, 3.0%) was added to the mixture, and mixed for 10 minutes. SO2 gas (0.4%) was introduced at a flow rate of 1°C / min in an 18 SCCM, and the polymerization was terminated when no further temperature rise was observed by monitoring the temperature change. 1.77 g of sodium metabisulfite (MBS) solution (30 wt%) was added to the reaction mixture and mixed for about 10 minutes, after which 10 g of the surfactant Tergitol L24-7 (1.43 wt%) was added and mixed for about 20 minutes to obtain a cationic polymer solution in the form of a reverse-phase emulsion.

[0160] The molecular weight of the above cationic polymer was measured using gel permeation chromatography, and polyethylene oxide was used as a standard material for molecular weight calculation. The weight-average molecular weight of the above cationic polymer was measured to be approximately 1,000,000 g / mol.

[0161] The bulk viscosity of the cationic polymer solution measured at a polymer concentration of 0.2 wt% was 492 cps, and the standard viscosity of a 1 M NaCl aqueous solution containing the cationic polymer at a concentration of 0.1 wt% was 2.59 cps. The bulk viscosity and standard viscosity were measured using a Brookfield viscometer with a UL adapter and a #62 spindle at 25°C and 60 rpm. The degree of branching of the cationic polymer calculated using Equation 1 was 190.

[0162] Preparation of amphoteric polymer solution

[0163] Fennobond DS 220 (Kemira Oyj) was used as the amphoteric polymer.

[0164] Preparation of starch composition

[0165] The starch composition according to the embodiments of the present invention may be prepared by mixing the cationic starch slurry and the cationic polymer solution, or by mixing the cationic starch slurry, the cationic polymer solution, and the amphoteric polymer solution.

[0166] The above cationic polymer solution has the form of a water-in-oil emulsion, and the cationic polymer has a low molecular weight, high degree of branching and charge, so it can be directly added to a cationic starch slurry without separate aging.

[0168] <Experimental Example 1>

[0169] Examples 1 to 3

[0170] A starch composition was prepared by adding and mixing a cationic polymer solution containing 1 wt% of a cationic polymer to a cationic starch slurry A containing 1 wt% of cationic starch at the content ratio (weight ratio of cationic polymer to cationic starch) shown in Table 1 below.

[0171] Example 4

[0172] A starch composition was prepared by adding and mixing a cationic polymer solution containing 1 wt% of a cationic polymer to a cationic starch slurry B containing 2 wt% of cationic starch at the content ratio (weight ratio of cationic polymer to cationic starch) shown in Table 1 below.

[0173] Viscosity measurement

[0174] The viscosity of the cationic starch slurry, cationic polymer solution, and each starch composition was measured at 50°C and 60 rpm using an AMETEK Brookfield viscometer with a UL-adapter and a 304 ss spindle.

[0176] Experimental Example Viscosity (cps) 1wt% cationic starch slurry A 45.5 2wt% cationic starch slurry B 50 1 wt% cationic polymer solution 64 Example 1 1 part by weight of cationic starch 0.5 parts by weight of cationic polymer 123.9 Example 2 1 part by weight of cationic starch 1 part by weight of cationic polymer 155.5 Example 3 1 part by weight of cationic starch 2 parts by weight of cationic polymer 144.5 Example 4 1 part by weight of cationic starch 1 part by weight of cationic polymer 200

[0178] Referring to Table 1 above, cationic starch slurries A and B have low viscosities of 45.5 cps and 50 cps, respectively, and it was confirmed that the cationic starch was reduced in molecular weight by cooking. On the other hand, referring to the starch compositions of Examples 1 to 4, it was confirmed that the viscosity of the starch composition increased significantly as the cationic starch slurry and cationic polymer solution were mixed.

[0179] Meanwhile, the viscosity of the starch composition had a value greater than the sum of the viscosity of the cationic starch slurry and the viscosity of the cationic polymer solution, and it can be confirmed that an additional increase in molecular weight and viscosity was induced as the cationic starch and cationic polymer formed a complex.

[0180] In addition, referring to Table 1 above, cationic starch slurry A, prepared by batch cooking, exhibited a viscosity of 45.5 cps at a solid content concentration of 1 wt%, whereas cationic starch slurry B, prepared by a jet cooker, exhibited a viscosity of 50 cps even at a solid content concentration of 2 wt%. It was confirmed that when cooking using a jet cooker, the cationic starch is fragmented more than when cooking using a batch, resulting in a further decrease in viscosity.

[0182] <Experimental Example 2>

[0183] manufacturing of hand seats

[0184] A concentrated stock was prepared consisting of 100% bleached hardwood kraft pulp (LBKP). The pulp was diluted to 0.54% using white water treated with 35 ppm of calcium ions and 150 ppm of sulfate ions. The pH of the diluted stock was adjusted to about 6.9 to about 7.1.

[0185] Fiber furnish was obtained by adding a starch composition having the compositions of Tables 2 and 3 below to the above stock. The content (parts by weight) of the cationic starch, cationic polymer, and amphoteric polymer added to the above stock was adjusted as shown in Tables 2 and 3 below based on 100 parts by weight of the above LBKP. Cationic starch slurry A was used as the source of the cationic starch.

[0186] Approximately 100 g / m² according to TAPPI T205 specifications 2 A hand sheet having a basis weight was manufactured.

[0187] The hand sheet obtained above was conditioned for 12 hours at room temperature and 50% relative humidity according to TAPPI T 402 om-93, standard conditioning and test atmosphere.

[0189] Measurement of tensile strength increase rate

[0190] A constant rate of elongation was applied to the samples, and the tensile strength of the handsheets was measured by referring to TAPPI test method T494. Twelve measurements were recorded for each cross direction per condition, and the average value was calculated. A Thwing-Albert QC3A series tensile tester was used for the tensile strength measurement.

[0191] Pure hand sheets made from stock without added starch composition (approx. 100 g / m²) 2 The tensile strength of the basis weight was measured. Based on the tensile strength of the pure hand sheet, the rate of increase in tensile strength of the hand sheets manufactured in each example and comparative example was calculated.

[0193] cationic starch (parts by weight) cationic polymer (parts by weight) Tensile strength increase rate (%) Comparative Example 1 0.5 0 1.28 Example 5 0.5 0.5 2.23 Example 6 0.5 1 4.99 Example 7 0.5 2 7.3 Comparative Example 2 1 0 4.95 Example 8 1 0.5 5.67 Example 9 1 1 10.04 Example 10 1 2 10.43 Comparative Example 3 1.5 0 9.30 Example 11 1.5 0.5 11.85 Example 12 1.5 1 12.65 Example 13 1.5 2 16.04

[0195] cationic starch (parts by weight) cationic polymer (parts by weight) Amphoteric polymer (parts by weight) Tensile strength increase rate (%) Comparative Example 2 1 0 0 4.95 Example 8 1 0.5 0 5.67 Example 9 1 1 0 10.04 Example 10 1 2 0 10.43 Comparative Example 4 1 0 0.1 8.32 Example 14 1 0.5 0.1 9.83 Example 15 1 1 0.1 10.05 Example 16 1 2 0.1 12.85 Comparative Example 5 1 0 0.3 10.68 Example 17 1 0.5 0.3 13.36 Example 18 1 1 0.3 13.90 Example 19 1 2 0.3 14.22 Comparative Example 6 1 0 0.5 13.26 Example 20 1 0.5 0.5 14.99 Example 21 1 1 0.5 18.17 Example 22 1 2 0.5 18.24

[0197] Referring to Table 2 above, it was confirmed that the increase in tensile strength was greater in Examples 5 to 13, in which a starch composition containing both cationic starch and cationic polymer was added, compared to Comparative Examples 1 to 3, in which a starch composition containing only cationic starch was added.

[0198] Referring to Table 3 above, it was confirmed that the tensile strength increase rate was improved in Examples 14 to 22, in which the starch composition further includes an amphoteric polymer along with cationic starch and a cationic polymer, compared to Examples 8 to 10. On the other hand, it was confirmed that the tensile strength increase rate was lower compared to the examples in Comparative Examples 4 to 6, in which the cationic polymer is not included and only cationic starch and an amphoteric polymer are included.

[0200] <Experimental Example 3>

[0201] manufacturing of hand seats

[0202] A hand sheet was prepared in the same manner as in Experimental Example 2, except that cationic starch slurry B was used as the source of the cationic starch. The content (parts by weight) of cationic starch and cationic polymer added to the stock was adjusted as shown in Table 4 below, based on 100 parts by weight of LBKP.

[0204] Measurement of tensile strength increase rate

[0205] The tensile strength of the hand sheet was measured in the same manner as in Experimental Example 2, and the rate of increase in the tensile strength of the hand sheet according to the example and comparative example was calculated relative to the tensile strength of the pure hand sheet.

[0207] Measurement of new growth rate

[0208] A constant rate of elongation was applied to the samples, and the elongation at break of the paper and cardboard was measured by referring to TAPPI test method T494. Twelve measurements were recorded for each cross direction per condition, and the average value was calculated. A Thwing-Albert QC3A series tensile tester was used to measure the elongation at break.

[0209] The rate of increase in the elongation of the hand sheet according to the examples and comparative examples was calculated relative to the elongation of the pure hand sheet.

[0211] cationic starch (parts by weight) cationic polymer (parts by weight) Tensile strength increase rate (%) New growth rate (%) Comparative Example 7 0.5 0 8.58 15.11 Example 23 0.5 1 9.21 27.53 Example 24 0.5 2 9.97 28.50 Comparative Example 8 1 0 11.77 37.86 Example 25 1 1 16.38 48.19 Example 26 1 2 18.38 53.06 Comparative Example 9 1.5 0 17.34 47.82 Example 27 1.5 1 21.47 58.02 Example 28 1.5 2 22.40 55.19

[0213] Referring to Table 4 above, it was confirmed that the tensile strength and elongation of the hand sheet increased further in Examples 23 to 28, in which a starch composition containing both cationic starch and cationic polymer was added, compared to Comparative Examples 7 to 9, in which a starch composition containing only cationic starch was added.

[0215] <Experimental Example 4>

[0216] manufacturing of hand seats

[0217] Adjust the composition of the fiber funish as shown in Table 5 below, and prepare a hand sheet (basis weight 100 g / m²) according to the TAPPI T205 standard. 2 ...was prepared. Cationic starch slurry A was used as the source of cationic starch. In Table 5 below, AKD (alkyl ketene dimer) is an emulsion-type sizing agent, bentonite was used as a drainage aid, and anionic micropolymer (M-polymer) was used as a retention polymer. The ash content in the hand sheet was measured to be 25% relative to 100% pulp (LBKP).

[0219] Measurement of internal bonding strength

[0220] The internal bond strength of the hand sheet was measured according to TAPPI T833 pm-94 using a HUYGEN internal bond tester. The internal bond strength was measured 10 times and calculated as the average value.

[0222] Tensile strength measurement

[0223] The tensile strength of the hand sheet was measured according to TAPPI T494 using a tensile testing machine (Thwing-Albert, QC3A series).

[0225] Folding endurance measurement

[0226] The cut strength of the hand seat was measured according to ASTM D 2176 using an MIT cut strength measuring instrument (CK-570DFT-4M, CKtrade).

[0228] Stiffness measurement

[0229] The bending stiffness of the hand seat was measured according to TAPPI T833 pm-94 using a Lorentzen & Wettre tensile testing machine.

[0231] Burst strength measurement

[0232] The rupture strength of the hand sheet was measured according to the TAPPI T403 test method.

[0234] division Comparative Example 10 Example 29 Example 30 Example 31 Example 32 Example 33 Example 34 Composition (weight part) LBKP 100 100 100 100 100 100 100 ASH 25 25 25 25 25 25 25 cationic starch 1.3 1.3 1.3 0.8 0.5 0.5 0.5 cationic polymer 0 2.0 2.0 2.0 2.0 2.0 2.0 amphoteric polymer 0.3 0 0.3 0.3 0.3 0.6 0.9 AKD 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Bentonite 0.3 0.3 0.3 0.3 0.3 0.3 0.3 M-polymer 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Physical properties Internal bond strength (IbFt) 127 136 146 141 131 137 140 Tensile strength (KN / m) 3.46 3.63 4.08 3.86 3.66 3.81 3.94 Internal severance (severance) 8 10 14 11 9 10 12 Stiffness (gCm) 0.65 0.69 0.74 0.71 0.68 0.71 0.75 Rupture strength (Kpa) 197 207 224 204 195 213 220

[0236] Referring to Table 5, it was confirmed that in the case of Comparative Example 10, which does not contain a cationic polymer, the quality of the hand sheet deteriorated overall even when cationic starch and amphoteric polymer were added together. Specifically, the internal bond strength between fibers was measured at 127 IbFt, and the tensile strength of the hand sheet was measured at 3.46 KN / m, the break resistance at 8 times, the stiffness at 0.65 gCm, and the burst strength at 197 Kpa.

[0237] On the other hand, in the case of Examples 29 and 30, as a specific cationic polymer was added along with cationic starch, the internal bonding strength between fibers was relatively high at 136 IbFt, and a hand sheet was provided having a tensile strength of 3.63 KN / m or more, a break resistance of 10 or more, a stiffness of 0.69 gCm or more, and a burst strength of 207 Kpa or more. Meanwhile, compared to Example 29, in the case of Example 30, the physical properties of the hand sheet were further improved as an amphoteric polymer was added along with the cationic polymer.

[0238] In the case of Examples 31 and 32, the amount of cationic starch added was reduced compared to Example 30, so the physical properties of the hand sheet were slightly degraded, but they still exhibited overall superior physical properties compared to the hand sheet of Comparative Example 10. In addition, in the case of Examples 33 and 34, the amount of amphoteric polymer added was increased compared to Example 32, so the physical properties of the hand sheet were further improved.

[0239] Accordingly, it has been confirmed that by using the cationic polymer according to the embodiments of the present invention, the interaction between the cationic starch and the fibers can be maximized, and consequently, the internal bonding strength between the fibers can be increased, thereby improving the mechanical properties of the final product.

[0240] For example, if the cationic polymer has a high weight-average molecular weight of more than 2,000,000 g / mol or has a linear structure, the tensile strength may be reduced by causing the cationic starch or fibers to clump together rather than networking the cationic starch and fibers together.

[0242] <Experimental Example 5>

[0243] The amphoteric polymer was diluted in water to a concentration of 10 wt% and stored for one day, and the transparency and precipitation of the diluted solution were observed. At this time, polyacrylamide-based polymers Fennobond 786 (Kemira Oyj) and Fennobond DS 220 (Kemira Oyj) were used as amphoteric polymers, respectively.

[0244] In Fennobond 786, the cation and anion charges were randomly distributed within the molecular structure, while in Fennobond DS 220, the cation and anion charge groups were distributed in localized regions within the molecular structure.

[0245] Figure 4a is a photographic image of a diluted solution of Fennobond 786, and Figure 4b is a photographic image of a diluted solution of Fennobond DS 220.

[0246] Referring to Figure 4a, the diluted solution was relatively transparent and no precipitation was observed. Therefore, it was confirmed that the amphoteric polymer was uniformly dissolved in the solution and no polyionic complex was formed.

[0247] Referring to Fig. 4b, the diluted solution was relatively opaque, and a precipitate was observed at the bottom. Thus, it was confirmed that the amphoteric polymers combined with each other to form a polyionic complex.

[0248] Therefore, it can be confirmed that when cationic charge groups and anionic charge groups are locally distributed within the molecular structure of the amphoteric polymer, the formation of a complex through the interaction of the amphoteric polymer becomes easier, which can further enhance adsorption to the fiber and increase the strength of the fiber. Explanation of the symbols

[0250] 10: Storage container 20: Mixing tank 30: Cooking Stage 40: Supply tank 50: Storage tank

Claims

Claim 1 A starch composition comprising: cationic starch; and a cationic polymer, wherein the cationic polymer is a copolymer of a monomer blend comprising an acrylamide-based monomer and a cationic monomer, the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the weight average molecular weight of the cationic polymer measured by GPC is 2,000,000 g / mol or less. Claim 2 In claim 1, the cationic polymer is a starch composition having a branched structure. Claim 3 A starch composition according to claim 1, wherein the viscosity of the starch composition at 50°C is 100 cps to 250 cps. Claim 4 A starch composition according to claim 1, wherein the content of the cationic polymer is 0.5 to 4.0 parts by weight per 1 part by weight of the cationic starch. Claim 5 A starch composition according to claim 1, wherein the starch composition further comprises an amphoteric polymer. Claim 6 In claim 5, the amphoteric polymer has a smaller molecular weight than the cationic polymer, in a starch composition. Claim 7 A starch composition according to claim 5, wherein the weight average molecular weight of the amphoteric polymer measured by the GPC method is 1,000,000 g / mol or less. Claim 8 A starch composition according to claim 5, wherein the weight average molecular weight of the amphoteric polymer measured by the GPC-MALS method is 3,000,000 g / mol to 5,000,000 g / mol. Claim 9 A starch composition according to claim 5, wherein the content of the amphoteric polymer is 0.1 to 2.0 parts by weight per 1 part by weight of the cationic starch. Claim 10 A method for preparing a starch composition, comprising: a step of obtaining a cationic starch slurry by cooking a starch mixture containing cationic starch and water; and a step of adding a cationic polymer solution to the cationic starch slurry, wherein the cationic polymer included in the cationic polymer solution is a copolymer of a monomer blend containing an acrylamide-based monomer and a cationic monomer, the content of the cationic monomer is 15 mol% to 50 mol% of the monomer blend, and the weight average molecular weight of the cationic polymer is 2,000,000 g / mol or less. Claim 11 A method for preparing a starch composition according to claim 10, wherein the viscosity of the starch composition at 50°C is 2 to 5 times the viscosity of the cationic starch slurry at 25°C. Claim 12 A method for preparing a starch composition according to claim 10, wherein the solid content concentration of the cationic polymer solution is 0.1% by weight to 1.0% by weight. Claim 13 A method for preparing a composition according to claim 10, wherein the cationic polymer solution has the form of an inverted emulsion. Claim 14 A method for preparing a starch composition according to claim 10, further comprising the step of adding an amphoteric polymer solution to the cationic starch slurry. Claim 15 A method for preparing a starch composition according to claim 14, wherein the solid content concentration of the amphoteric polymer solution is 15% to 30% by weight. Claim 16 A method for preparing a starch composition according to claim 14, wherein the pH of the amphoteric polymer solution at 25°C is 2.5 to 3.

5. Claim 17 A method for preparing a starch composition according to claim 14, wherein the viscosity of the amphoteric polymer solution is 6,000 cps to 12,000 cps at 25 ℃. Claim 18 A paper strength enhancer comprising a starch composition according to claim 1.

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