Starch-based highly-dilutable adhesive for tissue laminates

Abstract

The present invention relates to an adhesive for a paper laminate, and more particularly to an adhesive for a tissue paper laminate including at least one tissue ply that is adhered to itself (e.g., folded back on itself) or to another surface (e.g., another tissue ply or non-woven, woven fabric substrate, etc.), the adhesive being a highly dilutable adhesive based on an aqueous starch containing at least one modified starch and having a viscosity as defined herein. Also included are the use and method of use of such an adhesive, products, particularly the laminates obtained by these methods and uses.

Description

【Technical Field】 【0001】 Field of the Invention The present invention relates to an adhesive for a paper laminate, and more particularly to an adhesive for a tissue paper laminate containing at least one tissue ply, which is adhered by itself (e.g., used by folding itself back) or adhered to another surface (e.g., another tissue ply or non-woven fabric, woven fabric substrate, etc.). The adhesive is an aqueous starch-based highly dilutable adhesive containing at least one modified starch and having a viscosity defined herein. 【Background Art】 【0002】 Background of the Invention Tissue products are almost always used in daily life. Toilet tissue, facial tissue, tissue wipes, and paper towels are examples of tissue products used in the home and industry. Tissue products can be made from a single lamina (or ply) or can be laminates (or multi-ply, or other laminations) formed from two or more plies. As used herein, the term "lamina" or "ply" refers to a single sheet of tissue paper, and the terms "laminate" or "multi-ply" or "laminated" are used to characterize paper made by combining multiple layers of single sheets or plies together or bonding them to another woven or non-woven substrate material to obtain a unitized material. As used herein, the term "tissue laminate" refers to a laminate that includes at least one ply of tissue paper unitized with another substrate or ply, which are well known and recognized by those skilled in the art. As used herein, the term "tissue paper" or "tissue" refers to a woven or non-woven substrate material that is a relatively low-weight sheet used as a sanitary product such as facial tissue and bathroom tissue, or paper towels. These may also be manufactured in condenser, carbonized, lapping, and cleaning grades. General characteristics can include one or more of softness, sufficient strength and absorbency, a clean appearance, and the absence of coarse abrasive particles. In a typical embodiment, the tissue may have a basis weight of up to about 50 grams per square meter, more typically about 11 to about 30 grams per square meter. 【0003】 Single-ply tissue products have several drawbacks. For example, single-ply tissue products are stiffer than dual-ply tissue products with the same total square footage. This increase in stiffness leads to the consumer perception that single-ply tissue products are not as soft as multi-ply tissue products and are thus less preferred. Laminated tissues with the same total square footage as single-ply tissue products can have a greater caliper. This increase in caliper leads to the consumer perception that the product is thick and of high quality. Also, to provide the consumer with the convenience of using a material of a predetermined length, the tissue laminate may be perforated at a preselected length. 【0004】 However, tissue laminates are subject to the effect of the skinning phenomenon. Skinning occurs when the laminas separate from each other and can no longer remain as an integrated laminate. For example, when attempting to reduce the packaging and transportation costs of tissue products, shear forces are applied to the laminas due to compression of the tissue products, and skinning can occur. Skinning can also occur during the converting operation of the tissue when the top sheet of the roll breaks as a result of friction in the contact area between the surface on the production line and the roll paper. It can also occur during handling by the consumer. In the case of perforated toilet tissue, if a part of the top sheet of the roll is torn or lost, the plies may become uneven along the perforations. 【0005】 In the related art, attempts have been made to bond tissue laminas to reduce or minimize delamination. One method is to apply mechanical forces (friction and compression) to engage the sheets so that they do not separate from each other. These forces are generated by piercing the laminate with pinholes at the edges of the knurls engraved on the steel rolls to bond the sheets, or by pressing wavy lines onto the tissue during embossing. Another method is to use adhesives to bond the laminas together. Such approaches are described, for example, in International Patent Publications WO 2005 / 021623 and WO 2010 / 015280. 【0006】 Tissue laminates made with water-soluble adhesives readily decompose when wet with water, as can occur, for example, when toilet tissue or facial tissue is discarded in the sewer. As a result, the adhesives used to bond the tissue laminas together are desirably water-based (solutions, dispersions, emulsions, latexes, etc.) and at least water-soluble (solutions) or somewhat water-dispersible. Also, for economic reasons, it is desirable to use water-based adhesives. 【0007】 A variety of aqueous adhesives for such purposes are known in the art. For example, from WO 2005 / 021623, these are typically based on any one of polyvinyl alcohol (PVOH), polyvinyl acetate, cellulose ether, acrylic, and polyurethane. Among these, PVOH-based adhesives are currently the mainstream technology in the market for laminates of tissues and towels. A wide variety of products with different viscosities, solids contents, and performances are commercially available. However, a major drawback of these adhesives is that they rely on fossil-derived raw materials and are thus not optimal from the perspective of sustainability or environmental issues. Therefore, it is desirable to replace these materials with materials from renewable resources. Furthermore, PVOH-based adhesives are prone to contamination by bacteria and fungi and thus require preservatives to enhance storage stability. The use of such preservatives, although common, always carries the risk of being restricted in terms of usability for reasons of toxicity and allergy not only in food applications but also in cosmetic applications or other applications where the tissue comes into contact with the user's skin. Additionally, in many fields where preservatives can be used, there is also a general tendency for consumers to prefer products without preservatives. 【0008】 US 6,379,447 B1 relates to a selected polysaccharide laminate or adhesive having high adhesive strength and low bleed characteristics and useful for multi-ply lightweight paper products. This patent is an aqueous, high-solids, polysaccharide adhesive composition for lightweight paper laminates, containing from about 15 to 50 weight % of starch or dextrin, or a blend of starch and dextrin as a continuous aqueous phase, wherein these dispersed starches and dextrins have: a) a zero-shear viscosity of 0.07 Pa·s at 120°F (49°C) and a shear rate of 0.1 s -1 with a solids content of about 26% (+ / -1%), and b) a shear thinning index of about 0.9 to 1.1, and the adhesive composition has a bleed time exceeding 15 seconds, all at a solids content of 26% (+ / -1%) and 49°C. 【0009】 WO 2014 / 003556 A1 relates to the field of paper coating, and more particularly to means and methods for providing at least one layer of pigment on paper using a film coating to obtain a good printable surface. The present invention also targets coated paper, including the paper and the coating composition for paper of the present invention with reduced or removed water thereon. This patent application discloses a method for preparing coated paper comprising the following steps: a) providing a pigment wetting coating formulation comprising water, 2 - 20 parts of a binder and 100 parts of a pigment, wherein at least 50% of the binder is * 10 5 ~1 * 10 6 characterized by a molecular weight of 0.5 - 10 【0010】 Dalton, having a molecular branching degree of at least 6%, and being a highly branched starch (HBS) obtained by treating gelatinized starch or a starch derivative with glycogen branching enzyme (EC 2.4.1.18); wherein at least 70% of the pigment is calcium carbonate; and 【0011】 b) applying the pigment wetting coating formulation to the paper by film coating and drying the coated paper. 【0010】 WO 2010 / 003054 A1 generally targets compositions comprising proteins and starches, as well as methods for manufacturing and using such compositions. In one aspect of the present invention, the composition is used as an adhesive, binder or coating agent. In a further aspect of the present invention, the composition is used in an adhesive to increase at least one of the viscosity or adhesive strength of the adhesive, binder or coating agent. This patent application discloses an adhesive composition or binder composition comprising about 1% - about 99% of a plant protein and about 1% - about 99% of a starch. 【0011】 US 2007 / 240823 A1 relates to the field of adhesives. More specifically, the present invention relates to an adhesive particularly suitable for bottle label applications. This patent application discloses an aqueous adhesive suitable for industrial bottle label applications, comprising a starch component and a protein component, wherein the starch component does not include leguminous starch having an amylose content of 25% or more, the protein component does not include casein or gelatin, and the adhesive does not include synthetic polymers. 【0012】 WO 2014 / 200344 A1 relates to an aqueous adhesive composition containing starch. This patent application discloses an aqueous adhesive composition comprising highly branched starch (HBS) obtained by treating starch or a starch derivative with glycogen branching enzyme (EC 2.4.1.18), and further comprising a carboxymethyl polysaccharide derivative. 【0013】 WO 95 / 35202 A1 relates to an adhesive bonding system for laminates such as cardboard products or other types of composite panels, and to panels manufactured by the method. This patent application discloses a method for bonding two essentially continuous layers of material comprising: providing an application device adapted to continuously extrude a number of laterally spaced-apart continuous beads of an adhesive material comprising a significantly gelatinized starch-containing composition, the composition being gelatinized in the application device to a viscosity exceeding 200 seconds as determined by the Stein-Hall cup method; extruding a significantly gelatinized starch-containing adhesive composition between the plies of the material; and pressing the plies together. 【Prior Art Documents】 【Patent Documents】 【0014】 【Patent Document 1】 International Application Publication No. 2005 / 021623 【Patent Document 2】 International Application Publication No. 2010 / 015280 【Patent Document 3】 International Publication No. 2005 / 021623 [Patent Document 4] U.S. Patent No. 6,379,447 [Patent Document 5] International Publication No. 2014 / 003556 [Patent Document 6] International Publication No. 2010 / 003054 [Patent Document 7] Specification of U.S. Patent Application Publication No. 2007 / 240823 [Patent Document 8] International Publication No. 2014 / 200344 [Patent Document 9] International Publication No. 95 / 35202 [Summary of the Invention] [Problems to be Solved by the Invention] 【0015】 Therefore, there is a need for a more sustainable alternative adhesive for tissue adhesion with a reduced content of fossil-derived components. Furthermore, it is particularly desirable if such an adhesive can be provided without the need for preservatives. For this reason, a novel adhesive that is bio-derived, sustainable, free of preservatives, highly dilutable, and exhibits excellent performance during application is desired. [Means for Solving the Problems] 【0016】 Summary of the Invention The present invention is based on the surprising finding of the inventors that the above object can be achieved by using an aqueous and highly dilutable starch-based adhesive composition having an alkaline pH, preferably to eliminate the need for preservatives. 【0017】 Accordingly, in a first aspect, the present invention is directed to a liquid aqueous adhesive composition comprising at least one modified starch in an amount of 2 to 60% by weight, preferably 5 to 50% by weight, based on the total weight of the composition, wherein the adhesive composition has a dynamic viscosity of 10,000 to 40,000 mPa * s, preferably 15,000 to 30,000 mPa * s, measured according to Brookfield at 23 °C (using a Brookfield viscometer RVT, spindle 6, 20 rpm). 【0018】 In another aspect, the present invention is characterized by using the liquid aqueous adhesive composition according to the present invention as an adhesive for primary adhesion, preferably as an adhesive for paper primary adhesion, more preferably as an adhesive for tissue paper primary adhesion. 【0019】 In a further aspect, the present invention is directed to a method for manufacturing a product comprising at least 2 plies, preferably 2 to 5 plies of tissue plies, more preferably tissue paper plies, the method comprising: (a) applying a liquid aqueous adhesive composition according to the present invention or a water dilution thereof to at least 2 plies of a first ply at an adhesive: water mass ratio of 1:1 to 1:15 or 1:1 to 1:11, preferably 1:4 to 1:8; and (b) adhering the first ply to a second ply with the adhesive obtained in (a), and optionally further adhering plies. 【0020】 The present invention further encompasses a product obtainable according to the method of the present invention, wherein the product is preferably a paper laminate, more preferably a tissue paper laminate. 【0021】 These and other aspects, features and advantages of the present invention will become apparent to those skilled in the art in the following detailed description and claims. Each feature from one aspect of the present invention can be used in other aspects of the present invention. Further, the examples included herein are intended to illustrate and exemplify the present invention and not to limit it, and in particular, the present invention is not limited to these examples. 【BEST MODE FOR CARRYING OUT THE INVENTION】 【0022】 As used herein, "at least one" refers to one or more, i.e., one, two, three, four, five, six, seven, eight, nine, or more species. In relation to a certain species, this term relates to the type of compound, not the total amount of the molecule. Thus, "at least one modified starch" means that, for example, without specifying the amount of each compound, it may contain only one type of modified starch or several types of modified starches. 【0023】 All percentages indicated herein with respect to a composition or formulation relate to weight % relative to the total weight of each composition or formulation, unless otherwise specifically indicated. A numerical range specified in the form "x to y" includes the specified values. When multiple preferred numerical ranges are specified in this form, it is understood that all ranges created by combining different endpoints are also included. 【0024】 A numerical range specified in the form "x to y" includes the specified values. When multiple preferred numerical ranges are specified in this form, it is natural that all ranges resulting from combinations of different endpoints are also included. 【0025】 Here, a numerical value specified without digits after the decimal point means, unless otherwise defined, the complete value specified with one digit after the decimal point, i.e., for example, 99% means 99.0%. 【0026】 The terms "about" or "approximately" in relation to a numerical value refer to a variation of ±10%, preferably ±5% or ±1% with respect to the given numerical value. 【0027】 When referring to molar mass herein, unless otherwise specified, this information always refers to the number average molar mass M nrefers to. The number-average molar mass can be measured, for example, by gel permeation chromatography (GPC) in accordance with DIN 55672-1:2007-08 using THF as the eluent. The weight-average molecular weight M w as well as M n can also be measured by GPC as described for M 【0028】 Detailed Description The present invention relates to a liquid aqueous adhesive composition comprising at least one modified starch in an amount of 2 to 60% by weight, preferably 5 to 50% by weight, based on the total weight of the composition, wherein the adhesive composition has a dynamic viscosity of 10,000 to 40,000 mPa * s, preferably 15,000 to 30,000 mPa * s at 23 °C (measured according to Brookfield using a Brookfield viscometer RVT, spindle 6, 20 rpm). 【0029】 As used in the context of this specification, "Liquid" relates to the property that the composition is liquid under standard conditions, i.e., at 20 °C and 1013 mbar. However, this term also includes pasty and gel-like compositions as well as liquids having non-Newtonian behavior such as a yield point. 【0030】 As used in the context of this specification, "aqueous" means that the composition contains water, i.e., as a solvent, typically as the main solvent or the only solvent. In various embodiments, this means that the water content is at least 50% by weight, preferably 60, 70, 80 or 90% by weight, based on the total solvent content. 【0031】 In some embodiments, while water is the main solvent, it may be preferable for the composition to further contain a small amount of an organic solvent, particularly an alcohol, more particularly a polyol, such as 1,2- or 1,3-propanediol, glycol or glycerol, especially glycerol. The amount of such an organic solvent is preferably 10% by weight or less, more preferably 5% by weight or less, based on the total weight of the composition. In a preferred embodiment, the composition contains an organic solvent, such as glycerol, which can also be obtained from renewable resources, such as plants, in an amount of about 0.1 to 5% by weight, preferably about 0.5 to 5% by weight. This organic solvent may preferably be the only additional solvent other than water. 【0032】 The water content in the adhesive of the present invention is preferably at least 40% by weight, typically 45 to 90% by weight, preferably 50 to 80% by weight or 55 to 80% by weight or 60 to 80% by weight. 【0033】 The adhesive of the present invention is preferably highly dilutable, that is, a formulation that can be used immediately after dilution with water can be obtained at a mass ratio of the adhesive to water of at least 1:1, preferably at least 1:2. Typical dilution ratios are up to 1:15, preferably up to 1:11 or 1:10 or 1:9, and the preferred range is 1:3 to 1:11, preferably 1:4 to 1:9 or 1:4 to 1:8, for example in the range of 1:4, 1:5, 1:6, 1:7 or 1:8. In various embodiments, it is preferable for the adhesive to be a concentrate, that is, to be diluted with water before use. Thus, the liquid aqueous adhesive composition according to the present invention is designed and intended to be diluted with water before use at an adhesive:water mass ratio of 1:1 to 1:11, preferably 1:4 to 1:8, in various embodiments. Due to these properties, the adhesive of the present invention is particularly suitable for use on converting lines. 【0034】 The diluent medium or diluent described in this specification is preferably water or at least an aqueous solvent, and contains water as the main component, that is, the diluent medium preferably contains at least 80% by weight or more, typically 90% by weight or more, for example, 95% to 100% by weight of water. The water used for dilution may be deionized water to avoid contamination with undesirable salts, solutes, or ions. 【0035】 The adhesive of the present invention is starch-based in that it contains at least one modified starch. The amount of starch generally ranges from 2 to 60% by weight. The lower limit is 2, 3, 4, 5, 6 or 7% by weight, and the upper limit is 60, 55, 50, 45, 40 or 35% by weight. The typical amount range is about 5 to about 50% by weight or about 5 to about 40% by weight based on the total weight of the adhesive composition, although it also depends on the type of starch used. These amounts are intended to include polysaccharides based on α-D-glucose, including amylose and amylopectin, in the context of the present invention. Thus, as long as they are present in such polysaccharides, enzymatically and chemically modified, degraded, and gelatinized starches are also covered. 【0036】 In various embodiments, the starch used may not completely dissolve in water. In such embodiments, the adhesive composition of the present invention has the form of a dispersion in which the aqueous solvent is the continuous phase and at least the modified starch is the dispersed phase. Thus, the adhesive composition has a solids content of 2 to 60% by weight, preferably 5 to 50% by weight, in various embodiments. 【0037】 Modified starch is, in various embodiments, starch that has been modified by (acid) hydrolysis, enzymatic or chemical modification or degradation, oxidation, or sonication. Suitable methods for starch degradation are well known and widely practiced in the art, and such starches are commercially available. In certain embodiments, the modified starch is starch obtained from acid hydrolysis or enzymatic modification / degradation. Such starches can be obtained by subjecting natural starches, such as those obtained from vegetables and plants, including starches having a high amylopectin content (waxy starches), particularly cereal starches, preferably corn, barley, wheat, or rice starch, tuber or root starches, preferably potato, sweet potato, or tapioca starch, legume starches, preferably pea or bean starch, and sago or amaranth starch, to hydrolysis conditions or treating them with enzymes. The starch may be amylose and may be degraded by acid hydrolysis to yield short-chain polysaccharides that are fragments of the original long polysaccharide molecules. Similarly, such fragments may be produced by enzymatic activity, such as by an amylase such as alpha-amylase. The modified starch of the present invention is not cellulose or modified cellulose. 【0038】 Naturally derived starches typically have an amylose content of 20-40% by weight, depending on the plant species from which they are obtained. This amylose content is also preferred in the context of the present invention. However, certain plant varieties also have starches rich in amylopectin (waxy starches), which may also be used in accordance with the present invention. Since these are already highly branched, the degree of branching can be further increased by the methods described herein. 【0039】 Methods for decomposing starch are well known in the art. Oxidizing agents for oxidative decomposition include, but are not limited to, chromic acid, permanganate, hydrogen peroxide, nitrogen dioxide, hypochlorite, periodate, and peracids such as peracetic acid. Hydrochloric acid, sulfuric acid, or phosphoric acid may be used as the acid for acid hydrolysis, and the use of other acids such as acetic acid, oxalic acid, sulfurous acid, perchloric acid, or trichloroacetic acid is also possible. Enzymes that can be used to decompose starch are alpha - amylase and beta - amylase, glucoamylase and degrading enzymes. 【0040】 The modified starch used according to the present invention is digested starch, decomposed starch or solubilized starch. Such starch is obtained by obtaining water - soluble starch by gelatinization of natural starch granules. In such a gelatinization process, intermolecular bonds or starch molecules are decomposed in the presence of water and heat, so that more hydrogen - bonding sites can participate in more water. As a result, the starch granules are more or less irreversibly dissolved in water, water acts as a plasticizer, and a polymer solution or dispersion is obtained. Such gelatinized starch is then chemically or enzymatically modified, decomposed, or rearranged. 【0041】 In the context of the present invention, starch has a dynamic viscosity, measured according to Brookfield (Brookfield RVT, spindle 7, 20 rpm), of less than 500,000 mPa * s when it is in a 40 wt% solution in deionized water at 20°C, and is considered to be sufficiently gelatinized. 【0042】 In various embodiments, the modified starch of the present invention is chemically or enzymatically modified by derivatizing the starch or increasing its branching. In some embodiments, the modified starch is thus not a (unmodified) starch hydrolyzate or starch fragment, but may be used as a starting product for further modification as described hereinbelow. The modified starch of the present invention is preferably obtained by chemical or enzymatic modification of native starch as described below. 【0043】 In various embodiments, the modified starch is selected from starch ethers, preferably alkyl ethers, alkenyl ethers, aryl ethers, arylalkyl ethers, cycloalkyl ethers and cycloalkenyl ethers, and the corresponding hydroxyethers. Corresponding hydroxyethers include corresponding hydroxyalkyl ethers, hydroxyalkenyl ethers and the like. The alkyl and alkenyl groups in such starch ethers are typically short-chain alkyl and alkenyl groups, such as C1-C6 alkyl(ene)yl groups, especially methyl, ethyl, propyl, and butyl groups including 1-propyl, 2-propyl, 1-butyl, 2-butyl, isobutyl and tert-butyl. The aryl group is preferably a C6-C14 aryl group, preferably a monocyclic group such as phenyl. Preferred arylalkyl groups include benzyl. Cycloalkyl(ene)yl groups include, but are not limited to, cyclohexyl and cyclohexenyl. 【0044】 In various embodiments, suitable starch ethers are selected from the group consisting of allyl ether, benzyl ether, hydroxyethyl ether, hydroxypropyl ether, hydroxybutyl ether, and 2-hydroxy-3-butenyl ether, with hydroxypropyl ether being particularly preferred. In various embodiments, the modified starch comprises, or consists of, a starch ether such as hydroxypropyl starch (CAS 9049-76-7). Hydroxypropyl starch may be produced, for example, by reacting starch, such as potato starch which is usually provided in the form of an aqueous solution, with propylene oxide in the presence of a base such as NaOH. 1,2-Propanediol (CAS 57-55-6) is also produced as a by-product in this reaction. Hydroxypropylated starch, such as hydroxypropylated extruded potato starch, is commercially available, for example, as Emcol HE (ex Emsland Group). 【0045】 In various embodiments, the modified starch is selected from, but not limited to, starch esters, preferably organic acid esters, such as esters of starch with C1-C20 mono- and dicarboxylic acids, including formic acid esters, acetic acid esters, propionic acid esters, butyric acid esters, dodecanoic acid esters, octadecenoic acid esters, alkyl succinates and alkenyl succinates. For succinic acid esters, the same definitions of the above alkyl and alkenyl groups apply. 【0046】 In a further embodiment, the modified starch includes amide, ketone, aldehyde, acetal and ketal, carboxylate, phosphate, sulfate, sulfonate, amine, and ammonium group-containing starch derivatives. Amides can be obtained by reacting carboxylated or acid-modified starch with an amine or ammonia, thereby obtaining the corresponding amide. Ketones, aldehydes, and carboxylates are obtained by oxidizing the hydroxyl groups present in the starch. Carboxylates, phosphates, sulfates, and sulfonates can be obtained by directly substituting the hydroxy group with any of a carboxylate, phosphate, sulfate, or sulfonate group, or by substituting with an organic moiety such as an alkyl group, alkenyl group, aryl group, arylalkyl group, or cycloalkyl(ene)yl group containing such carboxylate, phosphate, sulfate, and sulfonate groups. Examples of the latter include, for example, carboxymethyl starch and carboxyethyl starch. Amines and ammonium-containing starches are obtained by substituting the hydroxy group with an amino group or an ammonium group. 【0047】 In various embodiments, the modified starch may be carboxymethyl starch or carboxyethyl starch, for example, carboxymethyl starch. Carboxymethyl starch obtained from corn starch is commercially available, for example, as Emprint CE (manufactured by Emsland Group). 【0048】 It is understood that in all of the modified starches described herein, the starch usually retains hydroxy groups, and thus the modification is only a partial modification. It is further contemplated that the modified starches described herein include any combination of the possible modifications described above. Thus, for example, the starch is hydroxypropyl-carboxymethyl starch. However, in some embodiments, the modified starch is not hydroxypropyl-carboxymethyl starch. 【0049】 In various preferred embodiments, the modified starch has a dynamic viscosity of less than 500,000 mPa·s as measured as a 40 wt% solution in deionized water at 20 °C according to Brookfield (Brookfield RSV, spindle 7 for viscosities above 50,000 mPa·s and spindle 6 for viscosities below 50,000 mPa·s, 20 rpm), and is an enzyme-modified starch obtained from native starch by modification with glycogen branching enzyme (EC 2.4.1.18). In a specific embodiment, the enzyme-modified starch has a dynamic viscosity of less than 200,000 mPa·s, preferably less than 100,000 mPa·s, more preferably less than 50,000 mPa·s, but preferably at least 10,000 mPa·s. A viscosity lower than 10,000 mPa·s may cause undesirable long process times and color instability. In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. * s for viscosities above 50,000 mPa·s and 50,000 mPa·s * s for viscosities below and 20 rpm), and is an enzyme-modified starch obtained from native starch by modification with glycogen branching enzyme (EC 2.4.1.18). In a specific embodiment, the enzyme-modified starch has a dynamic viscosity of less than 200,000 mPa·s, preferably less than 100,000 mPa·s, more preferably less than 50,000 mPa·s, but preferably at least 10,000 mPa·s. A viscosity lower than 10,000 mPa·s may cause undesirable long process times and color instability. In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. * s and is an enzyme-modified starch obtained from native starch by modification with glycogen branching enzyme (EC 2.4.1.18). In a specific embodiment, the enzyme-modified starch has a dynamic viscosity of less than 200,000 mPa·s, preferably less than 100,000 mPa·s, more preferably less than 50,000 mPa·s, but preferably at least 10,000 mPa·s. A viscosity lower than 10,000 mPa·s may cause undesirable long process times and color instability. In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. * s, preferably less than 100,000 mPa·s * s, more preferably less than 50,000 mPa·s * s, but preferably at least 10,000 mPa·s * s. A viscosity lower than 10,000 mPa·s may cause undesirable long process times and color instability. In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. * s may cause undesirable long process times and color instability. In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. * In a preferred range of less than 200,000 mPa·s, gelling and recrystallization are suppressed, which is preferred. 【0050】 Such enzyme-modified starches may be selected from cereal starches, preferably corn, barley, wheat, or rice starches, tuber or root starches, preferably potato, sweet potato, cassava, or tapioca starches, legume starches, preferably pea or bean starches, and sago and amaranth starches, said starches including the waxy starches derived from said plants, and more preferably may be potato starch. 【0051】 To obtain the above-described enzyme-modified starch, the starch may be gelatinized as described above and then treated with glycogen branching enzyme, particularly an enzyme of EC class 2.4.1.18. 【0052】 Native starch is composed of two components: substantially linear amylose with α-1,4 glycosidic bonds and branched α-1,6 branched amylopectin. Branching enzymes are enzymes that can convert α-1,4-glycosidic bonds into α-1,6-glycosidic bonds, thus creating additional branch points. During incubation of such an enzyme with starch, the linear structure is disrupted by cleaving the 1,4-glycosidic bonds, and the fragments of the linear molecules thus obtained migrate to new branch points by forming new alpha-1,6-glycosidic bonds. This results in a shorter average side chain length and a significant reduction in the ability of the newly branched molecules to interact intermolecularly. The starch thus obtained has many functional properties such as low viscosity at high concentrations, little or no retrogradation, transparency of the solution, and sufficiently high wet adhesiveness. 【0053】 Accordingly, the present invention also relates to the use of such (gelatinized) enzymatically modified starch having a dynamic viscosity of less than 500,000 mPa.s when measured as a 40 wt% solution in deionized water at 20 °C according to Brookfield (Brookfield RSV, spindle 7 for viscosities above 50,000 mPa.s and spindle 6 for viscosities below 50,000 mPa.s, 20 rpm). The degree of branching can vary and is determined by the desired application. Generally, the gelatinized enzymatically modified starch has a molecular branching level of at least 4%. In a preferred embodiment, the gelatinized enzymatically modified starch has a molecular branching level of at least 5.0%, more preferably at least 5.5%, or in the range of 5.5 - 6.5%. The molecular branching level referred to here is the amount of α-1,6-glycosidic bonds relative to the total amount of α-1,4-glycosidic bonds and α-1,6-glycosidic bonds (α-1,6 / (α-1,6 + α-1,4)) * * s above, and spindle 6 for viscosities of 50,000 mPa * s or less, 20 rpm) and measured as a 40 wt% solution in deionized water at 20 °C, having a dynamic viscosity of less than 500,000 mPa * s. Such (gelatinized) enzymatically modified starch is obtained from native starch by modification with glycogen branching enzyme (EC 2.4.1.18). *It means 100%), and can be determined according to methods known in the art. Usually, the upper limit of branching is about 8.0%, preferably 7.5% or less. 【0054】 Before contacting with the branching enzyme, the starch or its derivative is preferably gelatinized as described above. The gelatinized starch can be adjusted to the desired pH by the addition of an acid or a base. After reaching the desired pH and temperature, the branching enzyme is added and the starch solution is maintained at a predetermined temperature that allows enzyme activity for a certain time required for branching. Alternatively, the enzyme can be added to an aqueous slurry of starch and heated to the desired temperature under agitation such as stirring. 【0055】 The branching enzyme may be obtained from any suitable microbial source. Preferably, it is a thermostable glycogen branching enzyme obtained from mesophilic or thermophilic bacteria, such as an enzyme obtained from Aquifex aeolicus, Anaerobranca gottschalkii or Rhodothermus obamensis. 【0056】 The enzyme-modified starch may contain additional starch molecules, including those that are not modified as described herein. In a preferred embodiment, the modified starch according to the invention comprises at least 65% by weight, preferably at least 80% by weight, more preferably at least 90% by weight of the total starch. 【0057】 The liquid aqueous adhesive composition of the present invention preferably has a pH in the range of 9.0 to 12.0, preferably 10.0 to 11.5, most preferably 10.5 to 11.5 (measured at 20 °C). This alkaline pH eliminates the need to add preservatives to prevent the growth of bacteria or fungi in the composition, for example, during long-term storage. Furthermore, such pH values have been found not to adversely affect the stability of the composition and its components. 【0058】 In various embodiments, the adhesive compositions of the present invention, particularly those having the pH values indicated above, thus do not contain preservatives, particularly formaldehyde-releasing compounds, compounds of the isothiazolinone family including chloro-, methyl- and benzo-isothiazolinones, and nitro compounds such as bronopol (2-bromo-2-nitro-1,3-propanediol), which may be toxic and irritating upon skin contact. In preferred embodiments, none of these compounds are included in the compositions of the present invention. As used in the context of this specification, "Free of" means that they are not intentionally added and the amount thereof in the composition is less than 1% by weight, preferably less than 0.5% by weight, or less than 0.1% by weight, or even less than 0.05% by weight (all based on the total weight of the composition), or the amount thereof is so small that it cannot be detected at all by conventional means. 【0059】 As described above herein, in addition to modified starch and water, the adhesive composition may further contain one or more of additives such as defoamers, humectants, pH adjusters, preservatives (although these are not particularly preferred), organic solvents (as detailed above), colorants, dyes, pigments, and fragrances, preferably defoamers, humectants, pH adjusters, and organic solvents. 【0060】 According to a particularly preferred embodiment of the present invention, the adhesive composition contains at least one defoamer. 【0061】 Suitable humectants may include long-chain diols such as heptanediol or octanediol. pH adjusters include hydroxides, particularly alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, etc., ammonia, organic acids such as acetic acid or citric acid, and inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, etc. Particularly preferred are hydroxides, particularly sodium hydroxide, citric acid, and sulfuric acid. 【0062】 When using preservatives, it is desirable that they are not those listed as toxic or irritating in this specification. In various examples, it may be beneficial to use agents that have a bacteriostatic effect as a side effect and are mainly used for other purposes, such as citric acid. In certain embodiments, a small amount of hydrogen peroxide may be added, which also has a beneficial effect on viscosity and functions as a bactericide. 【0063】 In some embodiments, the adhesive composition contains citric acid or its salts, preferably in an amount of 0.5 to 3% by weight, for example 1.0 to 2.5% by weight. In such embodiments, citric acid may be used. 【0064】 When a defoaming agent is present, it is usually used in an amount of up to 1% by weight, for example up to 0.7% by weight or up to 0.5% by weight, for example at least 0.1% by weight. In various embodiments, the adhesive is not a foaming adhesive and is not used in the form of a foam during application. To ensure this non-foaming property, it may be preferable to include a defoaming agent. 【0065】 Sodium hydroxide may be used in an amount of 0.01 to 5% by weight, determined by the amount required to obtain the desired pH. The same applies to mineral acids such as sulfuric acid. 【0066】 Hydrogen peroxide may be used in an absolute amount of 0.01 to 0.1% by weight, typically in the form of a solution in water (about 35%). 【0067】 All of the above amounts are based on the total weight of the adhesive composition. 【0068】 In various embodiments, the total amount of additives / additional components as described above does not exceed 15% by weight, preferably at most 10% by weight or at most 8% by weight, based on the total weight of the composition. 【0069】 The adhesive composition described in this specification is preferably used as an adhesive for primary bonding, more preferably as an adhesive for paper priming, and even more preferably as an adhesive for tissue paper priming, and such use also forms part of the present invention. In such a primary bonding process, 2 to 5 plies may be bonded, preferably 2, 3 or 4 plies may be bonded. The plies may be fibrous webs including woven and non-woven fabrics, typically tissue plies, preferably paper tissue plies. Such tissue plies may be those commonly used for toilet paper, kitchen paper, paper towels, facial tissues, cosmetic wipes, paper handkerchiefs, etc. 【0070】 As described above for the adhesive, even in such applications, the adhesives described herein are typically used as aqueous dilutions in water at an adhesive:water mass ratio of 1:1 to 1:15 or 1:1 to 1:11, preferably 1:4 to 1:8. 【0071】 The present invention further relates to a method for manufacturing a product comprising at least 2 plies, preferably 2 to 5 tissue plies, more preferably tissue paper plies, the method comprising the following steps: (a) applying the liquid aqueous adhesive composition according to any one of claims 1 to 11 or an aqueous dilution thereof to a first ply of at least 2 plies at an adhesive:water mass ratio of 1:1 to 1:15, or 1:1 to 1:11, preferably 1:4 to 1:8; and (b) bonding the first ply to a second ply with the adhesive obtained in (a), and optionally further bonding plies. 【0072】 In such a method, the production line speed is 5 to 600 m / min, for example 50 to 600 m / min, preferably at least 100 m / min, and the preferred range is 450 to 600 m / min. The "line speed" relates to the total length of the plies bonded per minute. The plies are usually provided in very large rolls, and the bonded tissue laminate is usually wound up again into a roll. 【0073】 In the method of the present invention, in step (b), it may further include applying pressure to bond two plies. The step of bringing the two plies into contact may include embossing the paper laminate, that is, step (b) may include embossing at least two plies before, during, and / or after bonding. 【0074】 The adhesive is generally diluted and thus penetrates the paper plies and has a viscosity that allows multiple plies that are already laminated to be bonded in a single step. The application of the adhesive may be carried out via an embosser, and the adhesive is applied to at least the protrusions or ridges of the embosser, and as a result, is applied to the plies during embossing via the embosser. 【0075】 The present invention also relates to products obtained according to the methods and uses described herein. Such products include, but are not limited to, paper laminates, preferably tissue paper laminates, such as multi-ply bathroom tissue, toilet paper, kitchen paper, paper towels, facial tissue, cosmetic wipes, paper handkerchiefs, etc. 【0076】 All embodiments disclosed herein in relation to the adhesive composition are equally applicable to the uses, methods, and products, and vice versa. The present invention is further illustrated by the following examples without being limited thereto. All documents cited herein are incorporated by reference in their entirety. 【Examples】 【0077】 The following formulations were prepared and successfully tested as tissue paper ply adhesives. The ingredients described were added in the specified order: 【0078】 【Table 1】 【0079】 Comparative Examples CE1 and CE2 do not conform to the claimed invention. 【0080】 When present, 3a, 3b, and 3c, and 3 * a, 3 * b and 3 * c were added as a premix. After each addition, the mixture was mixed if necessary. After the addition of 3a, 3b, and 3c, it was heated to 70 °C and maintained at this temperature during the addition of 4. Before adding 8 and 9, the viscosity, pH, and solids content were measured and 8 and 9 were added if necessary. 【0081】 Adhesive formulation 3 was used with an applicator system (a tissue laminator with a DESL embossing unit) to bond 2 or 3 plies of 19 gsm (total 57 gsm) at a dilution rate of up to 1:8 with water to produce kitchen paper at a line speed of up to 500 m / min, and 2 or 3 plies of 15 gsm at a dilution rate of up to 1:11 with water to produce toilet paper at a line speed of up to 600 m / min, and was successfully tested. 【0082】 【Table 2】 【0083】 Market standard Comparative Example CE1 shows acceptable performance in use in a machine at a dilution with water of up to 1:6. The adhesion of the tissue plies in the final product is sufficient and the machine operates at the same speed as described for the invention without serious problems. However, most of the PVOH is not a renewable resource and requires preservatives, so the bio-based content is very low (less than 10%). Therefore, Comparative Example CE1 does not meet the requirements for the bio-based sustainable preservative-free adhesives targeted in the present invention. 【0084】 Comparative Example CE2 is based on the tapioca dextrin described in Patent US6,379,447 B1, but it could only operate at a maximum speed of 500 m / min. The final product had sufficient adhesiveness. However, to achieve this effect, a much higher solids content during use (26%) was required, which would have a negative impact on the sustainability assessment. The solids concentration could not be lowered. This is because if the adhesiveness drops below an appropriate limit, it will lead to the peeling of the paper ply, and the viscosity is too low for the adhesive to be transferred well to the roller and ultimately to the paper substrate. Another drawback of Comparative Example CE2 is that the adhesive is invaded by bacteria and fungi in the short term, so a storage system is required. This not only has an adverse effect on the final performance in consumer products and may lead to the contamination of the entire product, but also limits the usable period of the adhesive to a very short period (less than a few days) until it becomes unusable and is discarded. 【0085】 On the other hand, Examples 1 and 1a according to the claimed invention can be diluted up to 1:5 (solids content during use of 5%) and still exhibit moderate adhesiveness and acceptable viscosity during use, so they are more sustainable products. They also have good stability and can be used for up to 5 months until the thickening effect starts and the structure of the concentrated adhesive becomes pasty. Contrary to Comparative Examples CE1 and CE2, these adhesives do not require a storage system but are still stable against possible contamination by fungi or bacteria. 【0086】 Examples 2 and 2a according to the claimed invention exhibit performance comparable to Examples 1 and 1a, but reduce the solids content during use to only 2%. Also, the usable period until the concentrated adhesive thickens into a paste was short (1 month). 【0087】 Example 3a according to the claimed invention *is the thickest adhesive with a solids content of 43%, but can be diluted with water at a ratio of up to 1:11, most preferably 1:8, and still provide very strong adhesive properties. In addition, the viscosity after dilution does not drop too much, and as a result, there are no problems with the machine. As also shown in Examples 1a and 2a, the addition of a preservative is not necessary. Therefore, this adhesive exhibits the same or similar performance at a still higher possible dilution rate compared to Comparative Example CE1 based on PVOH. At the same time, this adhesive has a very high bio-based content of over 80%. Compared to the bio-based solution of Patent US 6379447 B1 (Comparative Example CE2), Example 3 shows better performance, allowing for a lower solids content during use and much higher dilution with water. At the same time, this adhesive can be used without adding a preservative, and in the challenge test, there are no problems due to bacterial or fungal contamination, indicating a significant improvement in the safety standards of the product.

Claims

[Claim 1] A liquid aqueous adhesive composition comprising at least one modified starch in an amount of 2 to 60% by weight, preferably 5 to 50% by weight, relative to the total weight of the composition, The adhesive composition has a viscosity of 10,000 to 40,000 mPa at 23°C (measured according to Brookfield standards using a Brookfield viscometer RVT, spindle 6, and 20 rpm). ＊ s, preferably 15,000 to 30,000 mPa ＊ A liquid aqueous adhesive composition having a dynamic viscosity of s. [Claim 2] The liquid aqueous adhesive composition according to claim 1, wherein the pH of the composition (measured at 20°C) is in the range of 9.0 to 12.0, preferably 10.0 to 11.5, and most preferably 10.5 to 11.

5. [Claim 3] The liquid aqueous adhesive composition according to claim 1, wherein the adhesive composition is diluted with water before use to a mass ratio of adhesive to water of 1:1 to 1:15 or 1:1 to 1:11, preferably 1:4 to 1:

8. [Claim 4] The liquid aqueous adhesive composition according to claim 1, wherein the modified starch is starch modified by (acid) hydrolysis, enzymatic or chemical modification or decomposition, oxidation, or sonication, preferably by enzymatic or chemical modification. [Claim 5] The liquid aqueous adhesive composition according to claim 1, wherein the modified starch is selected from starch ethers, preferably alkyl, alkenyl, aryl, arylalkyl, cycloalkyl and cycloalkenyl ethers, or corresponding hydroxy ethers, starch esters, preferably organic acid esters, amides, ketones, aldehydes, acetals and ketals, carboxylates, phosphates, sulfates, sulfonates, amines and ammonium group-containing starch derivatives, and combinations thereof. [Claim 6] The modified starch is selected from starch ethers selected from allyl ether, benzyl ether, hydroxyethyl ether, hydroxypropyl ether, hydroxybutyl ether, 2-hydroxy-3-butenyl ether, and carboxymethyl ether; starch esters selected from formic acid esters, acetate esters, propionic acid esters, butyrate esters, dodecanoic acid esters, octadecenoic acid esters, alkyl succinate esters, and alkenyl succinate esters; carboxylates, ketones, and aldehydes, more preferably hydroxypropyl ether and carboxymethyl ether, most preferably hydroxypropyl ether, as described in claim 1. [Claim 7] Modified starch is Brookfield (Brookfield RVT, 50,000 mPa) ＊ For viscosities greater than s, spindle 7 and 50,000 mPa ＊ For viscosities below s, the viscosity was measured according to a spindle of 6 and 20 rpm as a 40 wt% solution in deionized water at 20°C, yielding 500,000 mPa. ＊ The liquid aqueous adhesive composition according to claim 1, having a dynamic viscosity of less than s, and being an enzyme-modified starch obtained by denaturing natural starch with glycogen branching enzyme (EC 2.4.1.18). [Claim 8] Enzyme-modified starch is, (1) Less than 200,000 mPa ＊ s, preferably less than 100,000 mPa ＊ s, more preferably less than 50,000 mPa ＊ s, but preferably at least 10,000 mPa ＊ having a dynamic viscosity of s; and / or (2) A liquid aqueous adhesive composition according to claim 7, which is selected from cereal starch, preferably corn, barley, wheat, or rice starch, tuber or root starch, preferably potato, sweet potato, cassava, or tapioca starch, leguminous plant starch, preferably pea or bean starch, and sago and amaranth starch, wherein the starch comprises waxy starch derived from the plant, and more preferably potato starch. [Claim 9] The liquid aqueous adhesive composition according to claim 1, wherein the composition does not contain a preservative. [Claim 10] The liquid aqueous adhesive composition according to claim 1, comprising an antifoaming agent, a humectant, a pH adjuster, a preservative, an organic solvent, a colorant, a pigment, and a fragrance, more preferably one or more additives preferably selected from an antifoaming agent, a humectant, a pH adjuster, and an organic solvent, wherein the total amount of additives is preferably 15% by weight or less. [Claim 11] The use of the liquid aqueous adhesive composition according to any one of claims 1 to 10 as an adhesive for bonding plies, preferably an adhesive for bonding paper plies, more preferably an adhesive for bonding tissue paper plies, wherein the paper optionally has 2 to 5 tissue plies, preferably 2, 3 or 4 tissue plies. [Claim 12] The use according to claim 11, wherein the liquid aqueous adhesive composition according to any one of claims 1 to 10 is used as an aqueous diluent in an adhesive:water mass ratio of 1:1 to 1:11, preferably 1:4 to 1:

8. [Claim 13] A method for manufacturing a product comprising at least two plies, preferably two to five tissue plies, more preferably paper plies, the method being as follows: (a) Applying the liquid aqueous adhesive composition according to any one of claims 1 to 10, or an aqueous dilution thereof in an adhesive:water mass ratio of 1:1 to 1:15 or 1:1 to 1:11, preferably 1:4 to 1:8, to the first ply of at least two plies; and (b) Adhere the first ply with the adhesive obtained in (a) to the second ply, and optionally to any further plies. A manufacturing method that includes this. [Claim 14] (1) The production line speed is 5 to 600 m / min, preferably 450 to 600 m / min; and / or (2) The method further comprises, in step (b), applying pressure to bond the two plies; and / or (3) Step (b) includes embossing at least two plies before, during, and / or after bonding, The method according to claim 13. [Claim 15] A product obtained according to the method of claim 13, wherein the product is preferably a paper laminate, more preferably a tissue paper laminate.