Sizing agent compositions and methods thereof

Abstract

This present disclosure is directed to a sizing agent composition, comprising: (a) modified starch; and (b) nanocellulose. The sizing agent composition according to the present invention has good stability, which can greatly enhance paper strength and improve paper properties, such as improving paper burst index, ring crush index, tensile index, paper printability and the like.

Description

SIZING AGENT COMPOSITIONS AND METHODS THEREOF by Qinyuan Chai Hui GeYangyi Lu Kai Hong HuangCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese Patent Application No. 202311247210.6, filed on September 25, 2023, the contents of which are hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention belongs to the technical field of papermaking, in particular, the present invention relates to a sizing agent composition used in the papermaking process, a preparation comprising the sizing agent composition, a method for preparing the sizing agent composition, and applications of the sizing agent composition. More particularly, the sizing agent composition is a surface sizing agent composition.BACKGROUND

[0003] This background information is provided for the purpose of making information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should it be construed, that any of the information disclosed herein constitutes prior art against the present invention.

[0004] In the papermaking process, the strength index of paper needs to be met. To keep the required strength, large quantities of dry strength agent are added into the wet-end of pulp. However, adding large quantities of dry strength agent presents some challenges, including the retention difficulty and potential risk to cause paper machine system disorder. Another way to increase paper strength is to coat a thin layer of chemistry onto a dry paper surface by coat rods. Theoretically, the retention of surface sizing should be 100%. The excessive starch solution can be collected and recycled. Additionally, adding chemicals to the dry-end pulp willdecrease the paper machine sensitivity and improve running stability. However, the starch surface strength agent has its own limitations. When the starch sizing amount reaches a certain level, the increase in strength will reach a plateau and will not improve further with the increase of sizing amount. And due to the dramatic viscosity increase with starch concentration, the amount of starch that can be coated onto paper surface is very limited.

[0005] Sizing is an important method for improving paper strength and other properties. However, the prior art lacks an efficient sizing agent composition that can improve the retention rate while also enhancing paper strength and other properties. In order to solve the problems in the prior art, the present invention provides such a novel sizing agent composition and methods of using the same.BRIEF DESCRIPTION OF THE FIGURES

[0006] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

[0007] FIG. 1. Figure 1 shows the effect of sizing agent compositions according to an embodiment of the present invention, having different weight ratios of nanocellulose dispersion / starch dry weight, on the burst index.

[0008] Particular non-limiting embodiments of the present invention will now be described with reference to accompanying drawings.DESCRIPTION

[0009] Definitions

[0010] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and alterations and modifications in the illustrated invention, andfurther applications of the principles of the invention as illustrated therein are herein contemplated as would normally occur to one skilled in the art to which the invention relates.

[0011] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0012] For the purpose of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims unless a contrary meaning is clearly intended (for example in the document where the term is originally used).

[0013] The use of “or” means “and / or” unless stated otherwise.

[0014] The use of “a” or “an” herein means “one or more” unless stated otherwise or where the use of “one or more” is clearly inappropriate.

[0015] The use of “comprise,” “comprises,” “comprising,” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term “comprising,” those skilled in the art would understand that, in some specific instances, the embodiment or embodiments can be alternatively described using the language “consisting essentially of’ and / or “consisting of.”

[0016] As used herein, the term “about” refers to a ±10% variation from the nominal value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0017] Any ranges given either in absolute terms or in approximate terms are intended to encompass both, and any definitions used herein are intended to be clarifying and not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples arereported as precisely as possible. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges (including all fractional and whole values) subsumed therein.

[0018] As used herein, the term “burst index” refers to a measurement of the amount of pressure or force required to break through a specific area of a paper material, and can be used interchangeably with “burst factor”.

[0019] As used herein, the term “ring crush index” refers to a measurement of the maximum compressive force per unit length that a narrow test piece bent into the form of a cylinder, or a ring, can withstand on its edge without failure under defined conditions.

[0020] In the invention, the term "optionally" means that the features (such as, components, and steps) defined by this term may or may not exist. For example, when referring to "optionally, instructions for use", it means that instructions for use may or may not exist in the technical solution under discussion, and so on.

[0021] Cellulose nanocrystal (CNC) is a nanocellulose material with a diameter of about Inm to about 20 nm and a length of about 100 nm to about 800 nm (such as, about 100 nm to about 500 nm, about 200 nm to about 800 nm). The CNC is usually needle-shaped or rod-shaped and has a high degree of crystallinity. The CNC may have an aspect ratio of greater than 5, for example, about 5 to about 200, such as about 5 to about 150, about 10 to about 180, about 20 to about 170, about 30 to about 140, about 50 to about 100, about 70 to about 130, or any numerical values or subranges therein.

[0022] Cellulose nanofibrils (CNF) are nanocellulose materials with a diameter of about 4 nm to about 80nm (such as, about 4 nm to about 10 nm, about 10 nm to about 30 nm, about 20 nm to about 80 nm) and a length of about 1 pm to about 20 pm (such as, about 1 pm to about 3 pm, about 1 pm to about 10 pm, about 1 pm to about 20 pm). The CNF is in the form of fibrils and is usually extracted from wooden raw materials by physical methods such as grinding and high-pressure homogenization. The aspect ratio of CNF is greater than 100, for example, about 100 to about 2000, such as about 120 to about 1800, about 150 to about 1500, about 200 toabout 1300, about 500 to about 1000, about 800 to about 1400, or any numerical values or subranges therein.

[0023] Microfibrillated cellulose (MFC) is a nanocellulose material with a diameter of less than 100 nm and a length of more than 20 gm (e.g., more than 30 gm). The MFC refers to an entangled network structure composed irregularly of numerous linear nanoscale microfibrils, which is a cellulose derivative.

[0024] In the present invention, the term "sizing solution" generally refers to the sizing agent composition described in the first aspect of the present invention, unless otherwise specified.

[0025] In the present invention, when referring to "the weight ratio between the nanocellulose dispersion added into the sizing agent composition and the dry weight of the modified starch" or similar expressions, it means the weight ratio between the weight of the nanocellulose dispersion used in preparing the sizing agent composition of the present invention and the dry weight of the starch used in preparing the composition, unless otherwise specified.

[0026] In the present invention, when referring to "the weight ratio between the nanocellulose and the modified starch in the sizing agent composition" or similar expressions, it means the weight ratio between the weight of the nanocellulose itself used in preparing the sizing agent composition of the present invention and the dry weight of the starch used in preparing the composition, unless otherwise specified.

[0027] In the present invention, when referring to "the modified starch is present in the sizing agent composition in an amount of about x wt% by weight" or similar expressions, it means that the dry weight of the modified starch used in preparing the composition accounts for about x wt% of the weight of the composition, unless otherwise specified.

[0028] In the present invention, when referring to "the modified starch and the nanocellulose are present in the sizing agent composition in an amount of about y wt% by weight" or similar expressions, it means that the sum of the dry weight of the modified starch and the dry weight of the nanocellulose used in preparing the composition accounts for about y wt% of the weight of the composition, unless otherwise specified.

[0029] In the present invention, when referring to "the nanocellulose is present in the sizing agent composition in an amount of about z wt% by weight" or similar expressions, it may also mean that the nanocellulose is present in the sizing agent composition in an amount of about z wt% by solid content, indicating that the weight of the nanocellulose itself used in preparing the composition accounts for about z wt% of the weight of the composition, unless otherwise specified.

[0030] In the present invention, "weight ratio of nanocellulose dispersion / dry weight of modified starch", "weight ratio between the nanocellulose dispersion and the dry weight of the modified starch" or "weight ratio of nanocellulose dispersion / absolute dry starch" or similar expressions, can be used interchangeably.

[0031] In the present invention, "nanocellulose dispersion" refers to a nanocellulose slurry formed by uniformly dispersing nanocellulose in water as the medium, with certain solid content.

[0032] In the present invention, unless otherwise defined, all other technical terms used herein will have the same meaning as those generally understood by ordinary technicians in the field to which the present invention belongs. The percentages mentioned are weight percentages unless otherwise specified.

[0033] Nanocellulose, including CNF, MFC, or CNC, is produced mainly using wood pulp as source material. The lateral dimensions of nanocellulose typically range from 5-20 nm, and the longitudinal dimensions can go up to hundred microns. During manufacturing, the pulp will be exposed to high shear forces to rip large wood-fibres apart into nanoscale fibers. The CNC has very high stiffness (140-220 GPa) comparable to Kevlar and even stronger than glass fiber, the latter two are both used as reinforcement for plastic matrixes. Benefiting from the chemical nature of nanocellulose, it has a chemical structure very similar to that of starch, with abundant hydroxyl groups on its surface. It has been found by the inventors that nanocellulose can be a natural reinforcement additive for starch with no interfacial modification required. The present application proves that nanocellulose is an efficient reinforcement additive for starch andtherefore can be used as a sizing agent composition in combination with starch, in particular, CNF and MFC or derivatives thereof (such as chemically modified CNF, chemically modified MFC) exhibit better performance.

[0034] In the present invention, the nanocellulose dispersion is added to an aqueous solution of starch with an optimized ratio to form a sizing agent composition. The sizing agent composition is applied onto various types of paper (including, for example, cardboard, graphic paper, and corrugated paper) to form a thin layer on the paper surface thereby providing the paper with desired properties.

[0035] As demonstrated in the following examples, it has been found by the inventors that the sizing agent composition of the present invention can greatly increase the burst index, ring crush index, and the like of the sized paper. In the meanwhile, the sizing agent composition of the present invention is able to achieve greater increase in paper strength with a smaller sizing amount relative to that of pure starch, can potentially reduce the amount of dry strength agent added to the wet-end, and thereby enabling lightweight papermaking.

[0036] In the sizing agent composition of the present invention, when nanocellulose (such as CNF, MFC, such as chemically modified CNF, chemically modified MFC) is mixed with starch in a high ratio (such as the weight ratio of the nanocellulose dispersion / dry weight of starch is about 100: 100, about 150:00, about 200: 100, about 250: 100, about 300: 100, about 350: 100, about 400:100, about 450: 100, about 500: 100 or any ranges or numerical values therein), it could also produce excellent reinforcement effects. For example, in the case of the above-described weight ratio of nanocellulose dispersion / dry weight of starch, when the sizing agent composition having a starch concentration of about 10 wt% to about 25 wt% (e.g., about 10 wt% to about 20wt%) is applied at a sizing amount of about 40 Kg / t, the sizing agent composition of the present invention is expected to produce a reinforcement effect of about 5% to about 15%; for example, the burst index is increased by about 5% to about 15% (such as, about 5% to about 12%, about 7% to about 14%, about 10% to about 13%, about 8%, about 9%, about 12%, about 15% or any subranges or numerical values therein), or the ring crushindex is increased by about 5% to about 15% (such as, about 5% to about 12%, about 7% to about 14%, about 10% to about 13%, about 8%, about 9%, about 12%, about 15% or any subranges or numerical values therein), and / or the tensile index is increased by about 5% to about 15% (such as, about 5% to about 12%, about 7% to about 14%, about 10% to about 13%, about 8%, about 9%, about 12%, about 15% or any subranges or numerical values therein).

[0037] It can be seen that the sizing agent composition of the present invention is highly efficient. It can be used with a size press to increase paper strength, improve retention rate, reduce air permeability, decrease the paper surface roughness and improve printability, offering broad application prospects.

[0038] SUMMARY

[0039] The present invention provides a novel sizing agent composition for papermaking, a preparation comprising the sizing agent composition, a method of using the sizing agent composition, preparation methods and applications of the sizing agent composition.

[0040] In a first aspect, the present invention provides a sizing agent composition, comprising: (a) modified starch; and (b) nanocellulose, wherein the nanocellulose has a diameter of about 1-100 nm, and a length of greater than or equal to about 1 pm.

[0041] In some embodiments, in the sizing agent composition, the weight ratio between the nanocellulose and the modified starch is about 0.005:100 to 60:100. In some embodiments, in the sizing agent composition, the weight ratio between the nanocellulose and the modified starch is about 0.005:100 to about 55:100, e.g., about 0.01:100 to about 50:100, about 0.01:100 to about 45:100, about 0.01:100 to about 40:100, about 0.01:100 to about 35:100, about 0.01:100 to about 30:100, about 0.015:100 to about 50:100, about 0.015:100 to about 45:100, about 0.015:100 to about 40:100, about 0.015:100 to about 20:100, about 0.02:100 to about 1:100, about 0.02:100 to about 1.5:100, about 0.02:100 to about 2.5:100, about 0.05:100 to about 0.5:100, about 0.05:100 to about 1:100, about 0.05:100 to about 2:100, about 0.05:100 to about 3:100, about 0.08:100 to about 1.2:100, about 0.08:100 to about 1.8:100, about 0.08:100 to about 3:100, about 0.1:100 to about 0.5:100, about 0.1:100 to about 1:100, about0.1:100 to about 2:100, about 0.1:100 to about 3.5:100, about 0.1:100 to about 4:100, about 0.1:100 to about 4.5:100, about 0.1:100 to about 5.5:100, about 0.1:100 to about 6:100, about 0.1:100 to about 7:100, about 0.2:100 to about 50:100, about 0.2:100 to about 45:100, about 0.2:100 to about 35:100, about 0.2: 100 to about 25:100, about 0.2: 100 to about 15:100, about 0.2:100 to about 5:100, about 0.3:100 to about 30:100, about 0.3:100 to about 20:100, about 0.3:100 to about 10:100, about 0.3:100 to about 8:100, about 0.3:100 to about 5:100, about 0.3:100 to about 3:100, about 0.3:100 to about 2:100, about 0.3:100 to about 1:100, about 0.5:100 to about 28:100, about 0.5:100 to about 18:100, about 0.5:100 to about 8:100, about 0.5:100 to about 0.8:100, about 0.8:100 to about 32:100, about 0.8:100 to about 22:100, about 0.8:100 to about 12:100, about 0.8:100 to about 2:100, about 1:100 to about 56:100, about 1:100 to about 46:100, about 1:100 to about 36:100, about 1:100 to about 26:100, about 1:100 to about 16: 100, about 1 : 100 to about 6: 100, about 1 : 100 to about 5: 100, about 1 : 100 to about 3:100, or any subranges or numerical values therein.

[0042] In some embodiments, the modified starch includes oxidized starch (e.g., oxidized corn starch, oxidized tapioca starch), enzymatic starch (e.g., enzymatic corn starch or enzymatic tapioca starch), cationic starch, or any combination thereof. In some embodiments, the modified starch is present in the sizing agent composition in an amount of about 5 wt% to about 30 wt% by weight, e.g., about 6 wt% to about 28 wt%, about 7 wt% to about 26 wt%, about 8 wt% to about 25 wt%, about 9 wt% to about 22 wt%, about 10 wt% to about 20 wt%, about 12 wt% to about 20 wt%, about 13 wt% to about 19 wt%, about 14 wt% to about 17 wt%, about 14 wt% to about 18 wt%, about 15 wt% to about 16 wt%, about 15 wt% to about 18 wt%, or any subranges or numerical values therein.

[0043] In some embodiments, the nanocellulose is present in the sizing agent composition in an amount of about 0.005 wt% wt% to about 3 wt% by weight (e.g., by solid content), e.g., about 0.005 wt% wt% to about 0.5 wt%, about 0.005 wt% wt% to about 1 wt%, about 0.005 wt% wt% to about 2 wt%, about 0.005 wt% wt% to about 2.5 wt%, about 0.005 wt% wt% to about 3 wt%, about 0.008 wt% wt% to about 0.4 wt%, about 0.01 wt% wt% to about 0.3 wt%,about 0.01 wt% wt% to about 0.5 wt%, about 0.01 wt% wt% to about 0.8 wt%, about 0.01 wt% wt% to about 1 wt%, about 0.01 wt% wt% to about 1.5 wt%, about 0.02 wt% wt% to about 0.2 wt%, about 0.02 wt% wt% to about 0.3 wt%, about 0.02 wt% wt% to about 0.6 wt%, about 0.02 wt% wt% to about 1.8 wt%, about 0.03 wt% wt% to about 0.3 wt%, about 0.05 wt% wt% to about 0.3 wt%, about 0.05 wt% wt% to about 0.5 wt%, about 0.05 wt% wt% to about 1 wt%, about 0.1 wt% wt% to about 1.2 wt%, about 0.5 wt% wt% to about 1.3 wt%, about 1 wt% wt% to about 2.5 wt%, about 2 wt% wt% to about 3 wt%, or any subranges or numerical values therein.

[0044] In some embodiments, in the sizing agent composition, the total content of the nanocellulose and the modified starch by weight (e.g., solid content) is about 5% wt% to about 45 wt%, e.g., about 5 wt% to about 40 wt%, about 5 wt% to about 33 wt%, about 6 wt% to about 35 wt%, about 7 wt% to about 20 wt%, about 7 wt% to about 30 wt%, about 8 wt% to about 28 wt%, about 9 wt% to about 25 wt%, about 10 wt% to about 15 wt%, about 10 wt% to about 20 wt%, about 10 wt% to about 28 wt%, about 10 wt% to about 30 wt%, about 10 wt% to about 35 wt%, about 11 wt% to about 25 wt%, about 12 wt% to about 18 wt%, about 12 wt% to about 23 wt%, about 13 wt% to about 20 wt%, about 14 wt% to about 17 wt%, about 14 wt% to about 18 wt%, about 15 wt% to about 17 wt%, or any subranges or numerical values therein.

[0045] In some embodiments, the nanocellulose comprises CNF, MFC, or a derivative thereof (e.g., modified CNF, modified MFC, e.g., carboxylated CNF) or any combination thereof. In some embodiments, the nanocellulose has a diameter of, such as about 1 nm to about 90 nm, about 1 nm to about 80 nm, about 4 nm to about 80 nm, about 5 nm to about 70 nm, about 10 nm to about 60 nm, about 15 nm to about 50 nm, about 20 nm to about 40 nm, about 25 nm to about 30 nm, about 1 nm to about 20 nm, about 4 nm to about 10 nm, 1 about 0 nm to about 30 nm, about 20 nm to about 80 nm, or any subranges or numerical values therein. In some embodiments, the nanocellulose has a length of, for example, about > 1 pm to less than 100 pm, such as about 1 nm to about 95 pm, about 1 nm to about 3 pm, about 1 nm to about 10 pm,about 15 nm to about 30 m, about 5 nm to about 20 pm, about 1 nm to about 20 pm, about 20 nm to about 30 pm, about 20 nm to about 50 pm, about 30 nm to about 70 pm, about 30 nm to about 80 pm, or any subranges or numerical values therein. In some embodiments, the nanocellulose has an aspect ratio (length / diameter) of greater than about 5, greater than about 30, greater than about 50, greater than about 100, greater than about 300, greater than about 500, greater than about 700, about 5 to about 200, 15 to about 150, 20 to about 120, 30 to about 100, 50 to about 90, 100 to about 2000, 150 to about 1800, about 230 to about 1500, about 500 to about 1000, about 450 to about 800, about 600 to about 900, about 550 to about 750, or any subranges or numerical values therein.

[0046] In some embodiments, when preparing the composition, the nanocellulose is added into the composition as a dispersion, wherein the weight ratio between the nanocellulose dispersion added into the composition and the dry weight of the modified starch in the sizing agent composition is about 1:100 to 500:100, such as about 5:100 to about 500:100, 5:100 to about 400:100, about 10:100 to about 50:100, about 10:100 to about 40:100. In some embodiments, the solid content of the nanocellulose in the nanocellulose dispersion is about 0.5 wt% to about 10 wt%. In some embodiments, the weight ratio between the nanocellulose dispersion added into the composition and the dry weight of the modified starch as added is about 5: 100 to about 500:100, such as about 5:100 to about 450:100, about 5:100 to about 350:100, about 5:100 to about 250:100, about 5:100 to about 150:100, about 10:100 to about 400:100, about 10:100 to about 300:100, about 10:100 to about 200:100, about 10:100 to about 100:100, about 10:100 to about 50:100, about 10:100 to about 40:100, about 10:100 to about 30:100, about 15:100 to about 40:100, about 15:100 to about 30:100, about 15:100 to about 20:100, about 20:100 to about 100:100, about 20:100 to about 80:100, about 20:100 to about 50:100, about 20:100 to about 40:100, about 25:100 to about 100:100, about 25:100 to about 75:100, about 25:100 to about 55:100, about 30:100 to about 60:100, about 35:100 to about 50:100, about 40:100 to about 60:100, about 50:100 to about 90:100, or any subranges or numerical values therein.

[0047] In some embodiments, the sizing agent composition comprises: (a) modified starch selected from oxidized starch, enzymatic starch and combinations thereof; and (b) nanocellulose selected from: CNF, MFC (e.g., CNF, chemically modified CNF such as carboxylated CNF, MFC, and chemically modified MFC) and any combination thereof, wherein the nanocellulose has a diameter of about 1-80 nm. In some embodiments, when preparing the composition, the nanocellulose is added into the composition as a dispersion, and the weight ratio between the nanocellulose dispersion added into the composition and the dry weight of the modified starch as added in the sizing agent composition is about 10: 100 to about 100: 100, such as about 10: 100 to about 40:100. In some embodiments, the solid content of the nanocellulose in the nanocellulose dispersion is about 0.5-10 wt%.

[0048] In some embodiments, the solid content of the nanocellulose in the nanocellulose dispersion is about 0.5 wt% to about 10 wt %, such as about 0.5 wt% to about 5 wt %, about 0.5 wt% to about 4.5 wt %, about 0.6 wt% to about 4 wt%, about 0.7 wt% to about 3 wt%, about 0.8 wt% to about 3.5 wt%, about 1 wt% to about 2 wt%, about 1 wt% to about 2.5 wt%, about 1 wt% to about 5 wt%, about 1.5 wt% to about 7 wt%, about 2 wt% to about 3 wt%, about 2 wt% to about 5 wt%, about 2.5 wt% to about 3.5 wt%, about 2.5 wt% to about 6 wt%, about 4 wt% to about 5 wt%, about 5 wt% to about 9 wt%, about 7 wt% to about 10 wt%, about 8 wt% to about 10 wt%, or any subranges or numerical values therein.

[0049] In some embodiments, the sizing agent composition comprises, consists of, or consists essentially of: (a) modified starch; (b) nanocellulose; and (c) a medium, such as water.

[0050] In some embodiments, the sizing agent composition further comprises one or more additional adjuvants, such as a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, and a retention aid, such as styrene acrylic emulsion, aluminum sulfate, silicone oil, sodium silicate, alkyl ketene dimer (AKD), acrylic emulsion, styrene maleic anhydride copolymer (SMA), ethylene maleic anhydride copolymer (EMA), polyaluminum chloride (PAC), wax emulsion, and rosin. In some embodiments, theadditional sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, AKD, SMA, EMA, PAC, wax emulsion, and rosin.

[0051] In some embodiments, the sizing agent composition comprises, consists of, or consists essentially of: (a) modified starch; (b) nanocellulose; (c) a medium (e.g., an aqueous medium, such as water); and (d) a preservative.

[0052] In some embodiments, the sizing agent composition is a surface sizing agent composition.

[0053] In some embodiments, the sizing agent composition is present in the form of a liquid (such as a solution, a suspension, an emulsion). Therefore, in some embodiments, the sizing agent composition of the present invention is also known as a sizing solution.

[0054] In some embodiments, the sizing solution has a viscosity of, for example, 5-1000 cps, as measured at a rotational speed of 30 rpm or 60 rpm with spindle No. 61, No. 62 or No. 63 under 65°C according to the Brookfield ASTM standard method. For example, the sizing solution has a viscosity of about 10 cps to about 150 cps, about 10 cps to about 200 cps, about 10 cps to about 950 cps, about 10 cps to about 1000 cps, about 30 cps to about 90 cps, about 40 cps to about 60 cps, about 40 cps to about 70 cps, about 40 cps to about 80 cps, about 50 cps to about 75 cps, about 50 cps to about 100 cps, about 50 cps to about 150 cps, about 50 cps to about 200 cps, about 50 cps to about 500 cps, about 50 cps to about 900 cps, about 100 cps to about 850 cps, about 150 cps to about 800 cps, about 200 cps to about 750 cps, about 250 cps to about 700 cps, about 300 cps to about 650 cps, about 350 cps to about 600 cps, about 400 cps to about 500 cps, or any subranges or numerical values therein.

[0055] In a second aspect, the present invention provides an additive preparation for papermaking, comprising the sizing agent composition described in the first aspect of the present invention and one or more additional additives. In some embodiments, the one or more additional additives are selected from: a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, a retention aid, etc., such as a silicone oil waterproofing agent, an alkenyl succinic anhydride sizing agent composition, anAKD surface sizing agent, a styrene acrylic emulsion, an acrylic emulsion, and SMA. In some embodiments, the additive preparation further comprises an additional reinforcing aid, as long as such chemicals have good compatibility with the sizing agent composition described in the first aspect of the present invention and do not cause significant changes in viscosity at a temperature of about 55-70°C.

[0056] In a third aspect, the present invention provides a method for using the sizing agent composition described in the first aspect of the present invention or the additive preparation described in the second aspect, comprising adding the sizing agent composition or the additive preparation into a paper machine system to coat the surface of a paper.

[0057] In some embodiments, the sizing agent composition or the additive preparation is applied by a paper dispenser.

[0058] In some embodiments, the method comprises: preheating the sizing agent composition or the additive preparation to 45 °C or higher (e.g., about 45 °C to about 85 °C, such as about 45 °C to about 70 °C, about 55 °C to about 65 °C, about 60 °C to about 75 °C, about 65 °C to about 80 °C, about 57 °C, about 59 °C, about 60 °C, about 62 °C, about 65 °C, about 68 °C, about 70 °C, about 72 °C, about 75 °C, about 78 °C, about 82 °C, or any subranges or numerical values therein) prior to applying it to the paper machine system. In some embodiments, the method comprises: controlling the sizing temperature of the paper machine at 45 °C to about 85 °C (such as about 50 °C °C to about 80 °C, about 55 °C °C to about 65 °C, about 60 °C °C to about 65 °C, about 65 °C °C to about 80 °C, about 57 °C, about 59 °C, about 62 °C, about 66 °C, about 67 °C, about 70 °C, about 72 °C, about 75 °C, about 78 °C, about 82 °C, or any subranges or numerical values therein) upon applying the sizing agent composition or additive preparation.

[0059] In some embodiments, the sizing agent composition or the additive preparation is applied onto a paper surface by means of an automatic rod coater, a size press, a coater, or a calendar.

[0060] In a fourth aspect, the present invention provides paper obtained using the sizing agent composition described in the first aspect of the present invention or the additive preparation described in the second aspect, for example, by the method according to the third aspect.

[0061] In a fifth aspect, the present invention provides a method for preparing the sizing agent composition according to the first aspect of the present invention, comprising: (1) providing a modified starch solution and (2) mixing nanocellulose dispersion with the modified starch solution thereby preparing the sizing agent composition.

[0062] In some embodiments, step (1) comprises cooking the modified starch at 75 °C to about 80 °C for about 15 min to about 60 min (such as about 15 min, about 20 min, about 25 min, about 30 min, about 35 min, about 40 min, about 45 min, about 50 min, about 55 min or any range, subranges or numerical values therein) to obtain a starch solution.

[0063] In some embodiments, when the modified starch is an enzymatic starch, step (1) is (T). In some embodiments, step (1') is carried out using a three-step batch cooking. For example, step (T) comprises: (la) adding starch and amylase into water and cooking at about 60 °C to about 65 °C for, for example, about 15 to about30 min (such as, about 15 to about 20 min, about 15 to about 25 min, about 20 to about 25 min); (lb) increasing the temperature to about 75 °C to about 80 °C and cooking for, for example, about 15 to about 240 min (such as, about 15to about 20 min, about 20 to about 150 min, about 30 to about 200 min, about 50 to about 250 min, about 25 to about 80 min or any subranges or numerical values therein); and (1c) increasing the temperature to 90 °C or higher (such as, about 92 °C, about 95 °C, about 98 °C, about 100 °C or higher) and inactivating the amylase.

[0064] In some embodiments, in the blend solution obtained in step (la), the starch concentration may be about 5 wt% to about 45 wt% (such as about 5 wt% to about 28 wt%, about 6 wt% to about 27wt%, about 7 wt% to about 25wt%, about 8 wt% to about 23 wt%, about 9 wt% to about 22 wt%, about 10 wt% to about 19 wt%, about 10 wt% to about 20wt%, about 10 wt% to about 35wt%, about 10 wt% to about 42wt%, about 11 wt% to about 16wt%, about 11 wt% to about 20wt%, about 10 wt% to about 28wt%, about 11 wt% to about 40wt%,about 12 wt% to about 18 wt%, about 12 wt% to about 30 wt%, about 13 wt% to about 14wt%, about 13 wt% to about 32wt%, about 15 wt% to about 17 wt%, about 15 wt% to about 38wt% or any ranges, subranges, or numerical values therein). In some embodiments, in step (la), the amylase is added in an amount of about 20 to about 150 ppm (such as, about 20 to about 140 ppm, about 25 to about 135 ppm, about 30 to about 130 ppm, about 50 to about 120 ppm, about 60 to about 100 ppm, about 70 to about 90 ppm or any range, subranges or numerical values therein) of dry starch. In some embodiments, the amylase used in step (la) is a mediumtemperature amylase conventionally used in the art.

[0065] In some embodiments, in step (1c), the temperature is maintained for 20 min or longer (such as, 25 min, 30 min or longer) upon being increased to 90 °C or above.

[0066] In some embodiments, step (T) further comprises step (Id): cooling the starch solution prepared in step (1c) to room temperature. In some embodiments, step (Id) further comprises: adding a medium (e.g., water) to the starch solution cooled to room temperature (e.g., below 40 °C) to maintain a desired starch concentration (e.g., about 5 wt% to about 45 wt%). In some embodiments, step (Id) further comprises: adding a preservative to the starch solution cooled to room temperature.

[0067] In some embodiments, when the modified starch is an oxidized starch or a cationic starch, step (1) is step (1"). In some embodiments, step (1") comprises: uniformly dispersing the oxidized starch or cationic starch into a medium (e.g., water) and heating the resulting blend solution. In some embodiments, said heating in step (1") comprises: cooking the blend solution at about 75 °C to about 80 °C for about 30 to about 40 min (such as, about 30 min, about 32 min, about 35 min, about 38 min, about 40 min, or any ranges, subranges, or numerical values therein) until the starch is completely gelatinized. In some embodiments, step (1") further comprises: cooling the gelatinized starch to room temperature to obtain a starch solution. In some embodiments, step (1") further comprises: adding a medium (e.g., water) to the starch solution cooled to room temperature (e.g., below 40 °C) to maintain a desired starchconcentration (e.g., about 5 wt% to about 45 wt%). In some embodiments, step (1") further comprises: adding a preservative to the cooled starch solution.

[0068] In some embodiments, the starch solution obtained in step (1) has a starch concentration of about 5 wt% to about 45 wt% (such as, about 5 wt% to about 28 wt%, about 6 wt% to about 27 wt%, about 7 wt% to about 25 wt%, about 8 wt% to about 23 wt%, about 9 wt% to about 22 wt%, about 10 wt% to about 19 wt%, about 10 wt% to about 20 wt%, about 10 wt% to about 35wt%, about 10 wt% to about 42 wt%, about 11 wt% to about 16 wt%, about 11 wt% to about 20 wt%, about 10 wt% to about 28 wt%, about 11 wt% to about 40 wt%, about 12 wt% to about 18 wt%, about 12 wt% to about 30 wt%, about 13 wt% to about 14 wt%, about 13 wt% to about 32 wt%, about 15 wt% to about 17 wt%, about 15 wt% to about 38 wt%, about 6 wt%, about 8 wt%, about 10 wt%, about 12 wt%, about 15 wt%, about 17 wt%, about 18 wt%, about 20 wt%, about 22 wt%, about 25 wt%, about 26 wt%, about 27 wt%, about 28 wt%, about 30 wt%, about 35 wt%, about 40 wt%, or any ranges, subranges, or numerical values therein). In some embodiments, the starch solution obtained in step (1) has a viscosity of about 5 to about 10000 cps (such as, about 10 to about 9000 cps, about 50 to about 8000 cps, about 100 to about 7000 cps, about 150 to about 6000 cps, about 200 to about 5000 cps, about 250 to about 4000 cps, about 300 to about 3000 cps, about 350 to about 2000 cps, about 400 to about 1000 cps, about 150 to about 7500 cps, about 250 to about 5500 cps, about 350 to about 4500 cps, about 450 to about 3500 cps, about 550 to about 2500 cps, about 650 to about 1500 cps, about 750 to about 1000 cps, or any subranges or numerical values therein).

[0069] In some embodiments, step (2) comprises mixing (e.g., in any proportion) the nanocellulose dispersion with the starch solution obtained in step (1) thereby forming a nanocellulose / starch complex (which may be, for example, in the form of a suspension), i.e., the sizing agent composition of the first aspect of the present invention.

[0070] In some embodiments, the solid content of the nanocellulose in the dispersion is about 0.5 wt% to about 10 wt %, such as, about 0.5 wt% to about 5 wt %, about 0.5 wt% to about 4.5 wt %, about 0.6 wt% to about 2 wt%, about 0.7 wt% to about 4 wt%, about 0.8 wt% to about3 wt%, about 0.9 wt% to about 3.5 wt%, about 1 wt% to about 4.5wt%, about 1 wt% to about 2 wt%, about 1 wt% to about 2.5 wt%, about 1 wt% to about 5 wt%, about 2 wt% to about 3 wt%, about 2 wt% to about 5 wt%, about 2.5 wt% to about 3.5 wt%, about 2 wt% to about 6 wt%, about 2.5 wt% to about 6 wt%, about 3 wt% to about 7 wt%, about 4 wt% to about 5 wt%, about 4 wt% to about 8 wt%, about 5 wt% to about 9 wt%, about 5 wt% to about 10 wt%, about 7 wt% to about 10 wt%, about 8 wt% to about 10 wt%, or any subranges or numerical values therein.

[0071] In a sixth aspect, the present invention provides use of the sizing agent composition or additive preparation as described above in the present invention in papermaking.

[0072] In another aspect, the present invention further provides a reagent kit, comprising the sizing agent composition in accordance with the various embodiments of the first aspect of the present invention or the additive preparation in accordance with the various embodiments of the second aspect and, optionally, instructions for use. In some embodiments, the reagent kit further comprises a preservative. In some embodiments, the modified starch and the nanocellulose (e.g., the nanocellulose dispersion) are packaged separately.

[0073] In embodiments of the above various aspects, the nanocellulose dispersion is an aqueous nanocellulose dispersion.

[0074] In embodiments of the above various aspects, the paper machine suitable for various aspects of the present invention is an eTAD paper machine or any other suitable papermaking machine known to those skilled in the art.

[0075] In embodiments of the above various aspects, the other or additional sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, AKD, SMA, EMA, PAC, wax emulsion, and rosin.

[0076] In embodiments of the above various aspects, the sizing agent composition (or sizing solution) or additive preparation of the present invention may be used by spraying, injection, coating, smearing, etc.

[0077] In embodiments of the above various aspects, the paper is common paper in the art, including but not limited to coated paper, white cardboard, cardboard paper, kraft paper, packaging paper, corrugated paper, offset paper, ordinary cultural paper, graphic paper, cardboard or any combination thereof.

[0078] In embodiments of the above various aspects, the source of the modified starch includes, but is not limited to, corn starch, tapioca starch, and potato starch.

[0079] The sizing agent composition according to the present invention has the following advantages: it can greatly enhance paper strength and improve paper properties, such as improving the burst index, ring crush index, printability, and the like of paper. Moreover, the sizing agent composition of the present invention also exhibits good stability, especially after the addition of a preservative, allowing for long-term (for example, more than two months) stable storage.

[0080] Other aspects and advantages of the invention will be apparent to those skilled in the art from reading the foregoing description.LIST OF EMBODIMENTSThe following is a non-limiting list of embodiments:1. A sizing agent composition for papermaking, comprising:(a) modified starch; and(b) nanocellulose, wherein the nanocellulose has a diameter in the range of about 1 nm to about 100 nm, and a length of greater than or equal to about 1 pm, and optionally, wherein the weight ratio between the nanocellulose and the modified starch in the sizing agent composition is in the range of about 0.005: 100 to about 60: 100, such as about 0.01 : 100 to about 50: 100, about 0.015: 100 to about 45: 100, about 0.2: 100to about 5: 100, or about 0.3: 100 to about 3: 100.2. The sizing agent composition according to embodiment 1, wherein the modified starch is present in an amount in the range of about 5 wt% to about 30 wt% by weight, such as about 10wt% to about 20 wt%, or about 14 wt% to about 18 wt% in the sizing agent composition; and wherein the nanocellulose is present in an amount in the range of about 0.005 wt% to about 3wt% by weight, such as about 0.01wt% to about lwt%, or about 0.01wt% to about 0.3wt% in the sizing agent composition.3. The sizing agent composition according to embodiment 1 or 2, wherein the nanocellulose comprises CNF, modified CNF, MFC, modified MFC or any combination thereof, and / or, wherein the modified starch comprises oxidized starch, enzymatic starch, cationic starch, or any combination thereof, optionally, wherein the modified starch and the nanocellulose are present in an amount in the range of about 5 wt% to about 40 wt%, such as about 10 wt% to about 35 wt%, or about 7 wt% to about 20 wt% by weight in the sizing agent composition.4. The sizing agent composition according to any one of embodiments 1-3, wherein the nanocellulose has a length in the range of about 1 pm to about 100 pm, optionally, wherein the nanocellulose has a diameter in the range of about 1 nm to about 80 nm, and optionally, wherein the sizing agent composition further comprises one or more additional additives selected from: a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, a retention aid, or any combination thereof.5. The sizing agent composition according to any one of embodiments 1-4, wherein the sizing agent composition is used for surface sizing, optionally, the sizing agent composition has a viscosity in the range of about 5 cps to about 1000 cps, such as about 50 cps to about 500 cps, as measured at a rotational speed of 30 rpm with spindle No. 62 under 65°C according to the Brookfield ASTM standard method.6. The sizing agent composition according to any one of embodiments 1-5, wherein when preparing the composition, the nanocellulose is added into the composition as a dispersion, wherein the weight ratio between the nanocellulose dispersion added into the composition and the dry weight of the modified starch in the sizing agent composition is in the range of about1 : 100 to about 500: 100, such as about 5: 100 to about 500: 100, about 5: 100 to about 400: 100, about 10:100 to about 50: 100, or about 10: 100 to about 40: 100, optionally, wherein the solid content of the nanocellulose in the nanocellulose dispersion is in the range of about 0.5 wt% to about 10 wt%, such as about 1 wt% to about 5 wt% or 7 wt% to about 10 wt%.7. An additive preparation for papermaking comprising the sizing agent composition of any one of embodiments 1-6 and one or more additional additives, optionally, wherein the one or more additional additives are selected from: a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, a retention aid or any combination thereof.8. The sizing agent composition according to embodiment 5 or the additive preparation according to embodiment 7, wherein the additional sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, alkyl ketene dimer (AKD), styrene maleic anhydride copolymer (SMA), ethylene maleic anhydride copolymer (EMA), polyaluminum chloride (PAC), wax emulsion, and rosin.9. A method for surface sizing using the sizing agent composition of any one of embodiments 1-6 and 8, or the additive preparation of any one of embodiments 7-8 in a papermaking process, comprising applying the sizing agent composition or additive preparation onto the surface of a paper, optionally, the sizing agent composition or additive preparation is applied by means of an automatic rod coater, size press, a coater, a calendar, or any combination thereof.10. The method according to embodiment 9, further comprising heating the sizing agent composition or additive preparation to a temperature in the range of about 45 °C to about 85 °C prior to application, optionally, the sizing temperature of paper machine is controlled at a temperature in the range of about 45 °C to about 85°C upon applying the sizing agent composition or additive preparation.11. A paper product or a paper, wherein said paper product or paper is obtained by the method according to embodiment 9 or 10.12. A method for preparing the sizing agent composition according to any one of embodiments1-6 and 8, comprising:(1) providing a modified starch solution (e.g., which has a viscosity in the range of about 5 cps to about lOOOOcps, and a concentration of the modified starch in the range of about 5 wt% to about 45wt%); and(2) mixing nanocellulose dispersion with the modified starch solution thereby preparing the sizing agent composition, optionally, wherein the solid content of the nanocellulose in the dispersion is in the range of about 0.5 wt% to about- 10 wt%.13. The method according to embodiment 12, wherein step (1) comprises cooling the resulting modified starch solution to room temperature, and adding a preservative thereto, optionally, step (1) further comprises adding amylase to the resulting modified starch solution, wherein said amylase has a concentration in the range of about 20 ppm to about 150 ppm based on the weight of dry modified starch.14. The sizing agent composition according to any one of embodiments 1-6, and 8, the additive preparation according to any one of embodiments 7-8, or the method any one of embodiments 9-10, and 12-13, wherein the sizing agent composition or additive preparation is suitable for paper selected from the group consisting of coated paper, white cardboard, cardboard paper, kraft paper, packaging paper, corrugated paper, offset paper, ordinary culture paper, graphic paper, cardboard or any combination thereof; or the paper according to embodiment 11, wherein said paper is selected from the group consisting of coated paper, white cardboard, cardboard paper, kraft paper, packaging paper, corrugated paper, offset paper, ordinary culture paper, graph paper, cardboard or any combination thereof.EXAMPLES

[0081] The following examples are provided solely to illustrate the present invention and are not intended to limit the scope of the invention, described herein.

[0082] The following components will be used in the examples:

[0083] (1) Nanocellulose

[0084] Table 1 lists the specific types of nanocellulose (dispersion) used in the examples, and related parameters thereof.

[0085] Table 1 : Types of nanocellulose

[0086] (2) Modified starch

[0087] Oxidized com starch, for example, a 10% aqueous solution, with a viscosity ranging from about 10 cps to about 100 cps at 65 °C.

[0088] Enzymatic corn starch (obtained by hydrolyzing native com starch with amylase), for example, a 15% aqueous solution, with a viscosity ranging from about 5 cps to about 300 cps at 65 °C.

[0089] The properties of formulations of the sizing agent composition prepared in accordance with the present invention and the paper properties were measured as follows:

[0090] (1) Burst index, measured in accordance with TAPPIT-403 standard;

[0091] (2) Ring crush index, measured in accordance with TAPPIT-818 standard;

[0092] (3) Tensile index, measured in accordance with TAPPIT-494 standard;

[0093] (4) Viscosity: all viscosities were measured on Brookfield viscometer, with spindle No. 2 or No. 3, at 30 rpm or 60 rpm;

[0094] (5) Percent of solid content (solid%), obtained by calculating the dry-wet weight ratio of about 5g of sample after being dried in a 105°C oven;

[0095] (6) Stability: the sample was stored at room temperature, and observed visually for the presence of stratification; changes in viscosity was measured, variation in emulsion particle size was tested, and samples were dried to test changes in solid content.

[0096] Example 1. Preparation of sizing agent composition

[0097] 1. Preparation of modified starch solution

[0098] (1) Enzymatic starch solution

[0099] 50-150 ppm of amylase was added to native com starch, and cooked at 60-65°C for 15- 60 min. The resulting solution was heated to 95°C or above to achieve high-temperature inactivation. The concentration of the enzymatic starch solution was finally controlled at 10- 40 wt%, and the viscosity was in the range of 5-10000 cps. Table 2 below shows various enzymatic starch solutions prepared in this example.

[0100] Table 2: Enzymatic starch solutions

[0101] (2) Oxidized starch solution

[0102] Corn starch was cooked at 80°C for 20 min to obtain a homogeneous starch solution. For example, the oxidized starch concentration was 10wt% and the viscosity was 30cps at 65°C.

[0103] 2. Preparation of sizing agent composition

[0104] The nanocellulose dispersion in Table 1 was mixed with the starch solutions obtained as described above in different ratios to obtain formulations of sizing agent composition (i.e., sizing solutions) having different starch and nanocellulose concentrations. When used, the sizing solution can be heated to 55-75°C. Table 3 shows some examples of formulations of sizing agent composition prepared in the present invention and related parameters, wherein the cellulose is CNF-1 and the starch is enzymatic starch.

[0105] Table 3: Formulations of sizing agent composition

[0106] 3. Stability of sizing agent composition

[0107] The sizing agent composition prepared in the present application was stored at room temperature, and the stability was evaluated by visual observation (whether there was stratification) and measurement of various properties (such as viscosity, emulsion particle size, and solid content). The results showed that the sizing agent composition of the present invention had excellent stability, as shown in Tables 4 and 5 below (for Table 4, oxidized starch was used; and for Table 5, enzymatic starch was used).

[0108] Table 4: Stability of formulations of sizing agent composition

[0109] Table 5: Stability of formulations of sizing agent composition

[0110] Example 2. Effect of different types of nanocellulose on paper properties

[0111] Different formulations of sizing agent composition were prepared by the method described in Example 1, using enzymatic com starch and various nanocellulose dispersions in Table 1, with a weight ratio of cellulose dispersion / absolute dry starch of 10:100 and a starch solid content of 15%. Pure enzymatic starch (without nanocellulose) was used as a blank control.

[0112] The prepared formulations were applied onto kraft paper at a sizing amount of 40 kg / ton, and the effect on paper properties was measured. The results are shown in Table 6 below.

[0113] Table 6: Effect of different types of nanocellulose on paper properties

[0114] It can be seen from Table 6 that compared with CNC, CNF and MFC are more suitable for compounding with enzymatic starch solution. With an appropriate amount of preservatives added, the formulations can be stored stably for a long time. However, CNC easily causes instability after being mixed with a starch solution.

[0115] Example 3. Effect of weight ratio of nanocellulose dispersion / dry weight of modified starch on paper properties

[0116] Different formulations of sizing agent composition were prepared by the method described in Example 1, using enzymatic corn starch and nanocellulose CNF-2 with weight ratios of cellulose dispersion / dry weight of starch being 5: 100, 10: 100, 15: 100, 20: 100, 30: 100, 40: 100, 50: 100, and 600: 100 (high concentration), respectively. Enzymatic corn starch (without nanocellulose) was used as a blank control.

[0117] The prepared formulations were applied onto corrugated paper to measure the effect on paper properties. The results are shown in Table 7 below.

[0118] Table 7: Effect of weight ratios of nanocellulose dispersion / dry weight of modified starch on paper properties

[0119] It can be seen from the test results that when the weight ratio of nanocellulose dispersion / dry weight of starch reaches even only 5: 100, an increase in the effects was achieved. For nanocellulose of different types and sizes, the appropriate weight ratio is in the range of 5: 100-50: 100, better in the range of 10: 100 and 40: 100, 20: 100 and 40: 100. The sized paper had excellent physical strength. When the weight ratio of nanocellulose dispersion / dry weight of starch exceeds 50:100, paper properties can also be enhanced, with an increase of 5- 15% in these properties. It has been found by the inventors that as the concentration of nanocellulose increases, flocculation may occur in the starch solution, and large cellulose flocs may block the gaps in the paper, hindering the sizing solution from penetrating into the interior of the paper, and affecting its reinforcement effect.

[0120] In addition, formulations of sizing agent composition, with different weight ratios of cellulose dispersion / dry weight of starch (5: 100, 10: 100, 20: 100, 30: 100, 40: 100), were prepared by the method described in Example 1, using enzymatic corn starch (Table 8, solid content: 14-15wt%), oxidized tapioca starch (Table 9, solid content: 1 l-12wt%), oxidized com starch (Table 10, solid content: 14-15wt%) and different types of nanocellulose,. Pure starch (without nanocellulose) was used as a blank control or a dry strength agent (amphoteric polyacrylamide) was used as a control.

[0121] The prepared formulations were applied onto cormgated paper or kraft paper, and the effect on the burst index was measured. The results are shown in Tables 8, 9 and 10 below.

[0122] Table 8: Effect of different dry weight ratios on the burst index of kraft paperAccording to Table 8, it can be seen that different ratios of nanocellulose / modified starch produce better properties than unmodified starch and dry strength agent added in the wet-end. The results are also shown in Figure 1.

[0123] Table 9: Effect of formulations of sizing agent composition on the properties of corrugated paper

[0124] Table 10: Effect of formulations of sizing agent composition on the properties of kraft paper

[0125] According to Table 9 and Table 10, it can be seen that CNF produces better properties when applied onto corrugated paper and kraft paper, and provides an increase in the burst index of both kraft paper and corrugated paper.

[0126] Example 4. Formulations of sizing agent composition of the present invention and their performance.Different formulations of sizing agent composition were prepared by the method described in Example 1, using enzymatic corn starch and different types of nanocellulose with weight ratios of cellulose dispersion / dry weight of starch being 1 : 100, 5: 100, 10: 100, 15: 100, 20: 100, 30: 100, and 50: 100, respectively. The prepared formulations of sizing agent composition are shown in Table 11 below.

[0127] Table 11: Formulations of sizing agent composition

[0128] The prepared formulations were applied onto kraft paper and the properties of the sized paper were measured. The results are shown in Table 12 below.

[0129] Table 12: Performance of formulations of sizing agent composition on the properties of kraft paper

[0130] The foregoing description of the embodiments is to facilitate understanding and application of the invention by those of ordinary skill in the art. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described here to other embodiments without creative work. Therefore, the invention is not limited to the specific embodiments disclosed herein, and improvements and modifications made by those skilled in the art based on the principles of the invention without departing from the scope of the invention should be within the scope of the invention.

[0131] All publications mentioned herein are incorporated by reference to the extent they support the present invention.

Claims

CLAIMSWe claim:

1. A sizing agent composition for papermaking, comprising:(a) modified starch; and(b) nanocellulose, wherein the nanocellulose has a diameter in the range of about 1 nm to about 100 nm, and a length of greater than or equal to about 1 pm, and optionally, wherein the weight ratio between the nanocellulose and the modified starch in the sizing agent composition is in the range of about 0.005: 100 to about 60: 100.

2. The sizing agent composition according to claim 1, wherein the modified starch is present in an amount in the range of about 5 wt% to about 30 wt% by weight in the sizing agent composition.

3. The sizing agent composition according to claim 1 or 2, wherein the nanocellulose comprises CNF, modified CNF, MFC, modified MFC or any combination thereof, optionally, wherein the modified starch and the nanocellulose are present in an amount in the range of about 5 wt% to about 40 wt%, or about 10 wt% to about 35 wt%, or about 7 wt% to about 20 wt% by weight in the sizing agent composition.

4. The sizing agent composition according to any one of claims 1-3, wherein the nanocellulose has a length in the range of about 1 pm to about 100 pm, optionally, wherein the nanocellulose has a diameter in the range of about 1 nm to about 80 nm.

5. The sizing agent composition according to any one of claims 1-4, wherein the sizing agent composition is used for surface sizing.

6. The sizing agent composition according to any one of claims 1-5, wherein when preparing the composition, the nanocellulose is added into the composition as a dispersion, wherein the weight ratio between the nanocellulose dispersion added into the composition and the dry weight of the modified starch in the sizing agent composition is in the range of about 1 : 100 to about 500:100.

7. An additive preparation for papermaking comprising the sizing agent composition of any one of claims 1-6 and one or more additional additives.

8. The sizing agent composition according to claim 5 or the additive preparation according to claim 7, wherein the additional sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, alkyl ketene dimer (AKD), styrene maleic anhydride copolymer (SMA), ethylene maleic anhydride copolymer (EMA), polyaluminum chloride (PAC), wax emulsion, and rosin.

9. A method for surface sizing using the sizing agent composition of any one of claims 1-6 and 8, or the additive preparation of any one of claims 7-8 in a papermaking process, comprising applying the sizing agent composition or additive preparation onto the surface of a paper, optionally, the sizing agent composition or additive preparation is applied by means of an automatic rod coater, size press, a coater, a calendar, or any combination thereof.

10. The method according to claim 9, further comprising heating the sizing agent composition or additive preparation to a temperature in the range of about 45 °C to about 85 °C prior to application, optionally, the sizing temperature of paper machine is controlled at a temperature in the range of about 45 °C to about 85°C upon applying the sizing agent composition or additive preparation.

11. A paper product or a paper, wherein said paper product or paper is obtained by the method according to claim 9 or 10.

12. A method for preparing the sizing agent composition according to any one of claims 1-6 and 8, comprising:(1) providing a modified starch solution (e.g., which has a viscosity in the range of about 5 cps to about lOOOOcps, and a concentration of the modified starch in the range of about 5 wt% to about 45wt%); and(2) mixing nanocellulose dispersion with the modified starch solution thereby preparing the sizing agent composition,13. The method according to claim 12, wherein step (1) comprises cooling the resulting modified starch solution to room temperature, and adding a preservative thereto, optionally, step (1) further comprises adding amylase to the resulting modified starch solution, wherein said amylase has a concentration in the range of about 20 ppm to about 150 ppm based on the weight of dry modified starch.

14. The sizing agent composition according to any of the preceding claims wherein the sizing agent composition further comprises one or more additional additives selected from: a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, a retention aid, or any combination thereof.

15. The sizing agent composition according to any of the preceding claims wherein the sizing agent composition has a viscosity in the range of about 5 cps to about 1000 cps, as measured at a rotational speed of 30 rpm with spindle No. 62 under 65°C according to the Brookfield ASTM standard method.

16. The sizing agent composition according to any of the preceding claims, wherein the solid content of the nanocellulose in the dispersion is in the range of about 0.5 wt% to about- 10 wt%.

17. The sizing agent composition according to any of the preceding claims, wherein the solid content of the nanocellulose in the nanocellulose dispersion is in the range of about 0.5 wt% to about 10 wt%, or about 1 wt% to about 5 wt% or about 7 wt% to about 10 wt%.

18. The additive preparation of claim 7, optionally, wherein the one or more additional additives are selected from: a preservative, an additional sizing agent, an adhesive, a filler, a painting, a waterproofing aid, a dry strength agent, a retention aid or any combination thereof.

19. The sizing agent composition according to any of the preceding claims, The sizing agent composition according to any of the preceding claims , the additive preparation according to any of the preceding claims, or the method any of the preceding claims, wherein the sizing agent composition or additive preparation is suitable for paper selected from the group consisting of coated paper, white cardboard, cardboard paper, kraft paper, packaging paper, corrugated paper, offset paper, ordinary culture paper, graphic paper, cardboard or any combination thereof; or the paper according to claim 11, wherein said paper is selected from the group consisting of coated paper, white cardboard, cardboard paper, kraft paper, packaging paper, corrugated paper, offset paper, ordinary culture paper, graph paper, cardboard or any combination thereof.

20. The sizing agent composition according to any of the preceding claims, wherein the weight ratio between the nanocellulose and the modified starch in the sizing agent composition is in the range of about 0.01 : 100 to about 50: 100, about 0.015: 100 to about 45: 100, about 0.2: 100to about 5: 100, or about 0.3: 100 to about 3: 100.

21. The sizing agent composition according to any of the preceding claims, wherein the sizing agent composition has a viscosity in the range of about 50 cps to about 500 cps, as measured at a rotational speed of 30 rpm with spindle No. 62 under 65°C according to the Brookfield ASTM standard method.

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