Novel sizing agent composition as well as preparation method and application thereof

Abstract

The invention discloses a sizing agent composition. The sizing agent composition comprises (a) modified starch; and (b) nanocellulose wherein the nanocellulose has a diameter of about 1 to 100 nm and a length of greater than or equal to about 1 [mu] m, and wherein the weight ratio of the nanocellulose to the modified starch in the sizing agent composition is about 0.005: 100 to 60: 100. The invention also discloses a preparation containing the sizing agent composition, and a use method, a preparation method and application of the sizing agent composition. The sizing agent composition disclosed by the invention has good stability, and can be used for remarkably enhancing the strength of paper and improving the performance of the paper, such as the burst index, the ring crush index, the tensile index, the printing performance and the like of the paper.

Description

Technical Field

[0001] The present invention belongs to the technical field of papermaking, and in particular, the present invention relates to a sizing agent composition used in a papermaking process, a formulation containing the sizing agent composition, a method for preparing the sizing agent composition, and an application of the sizing agent composition. More particularly, the sizing agent composition is a surface sizing agent composition. Background Art

[0002] In the papermaking process, the strength index of paper needs to be met. In order to maintain the required strength, a large amount of dry strength agent is usually added to the wet end of the pulp. However, the addition of a large amount of dry strength agent brings some challenges, including the difficulty of retaining the added dry strength agent and the potential risk of causing paper machine system failure. Another way to improve paper strength is to apply a thin layer of chemicals on the dry paper surface with a coating rod. In theory, the retention rate of surface sizing should be 100%, and the excess starch solution can be recovered and recycled; moreover, adding chemicals to the dry end will reduce the sensitivity of the paper machine and improve the operation stability. However, starch surface strength agents have their own limitations. When the starch sizing amount reaches a certain level, the strength increase will enter a stable stage and will no longer increase with the increase of sizing amount. Moreover, since the viscosity increases sharply with the increase of starch concentration, the amount of starch that can be applied to the surface of paper is very limited.

[0003] Although sizing is an important means to improve paper strength and other properties, the prior art lacks an efficient sizing agent composition that can improve retention rate while improving 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 a method of using the same. Summary of the invention

[0004] The invention provides a novel sizing agent composition for papermaking, a preparation containing the same, a use method, a preparation method and an application of the sizing agent composition.

[0005] A first aspect of 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 about 1 μm or more.

[0006] In some embodiments, the weight ratio of the nanocellulose to the modified starch in the sizing agent composition is about 0.005:100-60:100. In some embodiments, the weight ratio of the nanocellulose to the modified starch in the sizing agent composition is about 0.005:100-55:100, for example, about 0.01:100-50:100, 0.01:100-45:100, 0.01:100-40:100, 0.01:100-35:100, 0.01:100-30:100, 0.015:100-50:100, 0.015:100-45:100, 0.015:100-40:100, 0.015:100-20:100, 0.02:100-1:100, 0.02:100-1.5:100. 100, 0.02:100-2.5:100, 0.05:100-0.5:100, 0.05:100-1:100, 0.05:100-2:100, 0.05:100-3:100, 0.08:100-1.2:100, 0.08:100-1.8:100, 0.08:100-3:100, 0.1:100-0.5:100, 0.1:100-1:100, 0.1:100-2:100, 0.1:100-3.5:100, 0.1:100-4:100, 0.1:100-4.5:100, 0.1:100-5.5: 100, 0.1:100-6:100, 0.1:100-7:100, 0.2:100-50:100, 0.2:100-45:100, 0.2:100-35:100, 0.2:100-25:100, 0.2:100-15:100, 0.2:100-5:100, 0.3:100-30:100, 0.3:100-20:100, 0.3:100-10:100, 0.3:100-8:100, 0.3:100-5:100, 0.3:100-3:100, 0.3:100-2:100, 0.3:100-1:10 0, 0.5:100-28:100, 0.5:100-18:100, 0.5:100-8:100, 0.5:100-0.8:100, 0.8:100-32:100, 0.8:100-22:100, 0.8:100-12:100, 0.8:100-2:100, 1:100-56:100, 1:100-46:100, 1:100-36:100, 1:100-26:100, 1:100-16:100, 1:100-6:100, 1:100-5:100, 1:100-3:100, or any sub-range or value therein.

[0007] In some embodiments, the modified starch comprises oxidized starch (e.g., oxidized corn starch, oxidized cassava starch), enzymatic starch (e.g., enzymatic corn starch or enzymatic cassava starch), cationic starch, or any combination thereof. In some embodiments, the modified starch is present in the sizing composition in an amount of about 5-30 wt% by weight, such as about 6-28 wt%, 7-26 wt%, 8-25 wt%, 9-22 wt%, 10-20 wt%, 12-20 wt%, 13-19 wt%, 14-17 wt%, 14-18 wt%, 15-16 wt%, 15-18 wt%, or any sub-range or value therein.

[0008] In some embodiments, the nanocellulose is present in the sizing composition in an amount of 0.005 wt%-3 wt% by weight (e.g., by solid content), for example, about 0.005 wt%-0.5 wt%, 0.005 wt%-1 wt%, 0.005 wt%-2 wt%, 0.005 wt%-2.5 wt%, 0.005 wt%-3 wt%, 0.008 wt%-0.4 wt%, 0.01 wt%-0.3 wt%, 0.01 wt%-0.5 wt%, 0.01 wt%-0.8 wt%, 0.01 wt%-0.9 wt%. %-1wt%, 0.01wt%-1.5wt%, 0.02wt%-0.2wt%, 0.02wt%-0.3wt%, 0.02wt%-0.6wt%, 0.02wt%-1.8wt%, 0.03wt%-0.3wt%, 0.05wt%-0.3wt%, 0.05wt%-0.5wt%, 0.05wt%-1wt%, 0.1wt%-1.2wt%, 0.5wt%-1.3wt%, 1wt%-2.5wt%, 2wt%-3wt% or any sub-range or value therein.

[0009] In some embodiments, in the sizing agent composition, the total content of the nanocellulose and the starch by weight (e.g., solid content) is about 5%-45wt%, for example, about 5-40wt%, 5-33wt%, 6-35wt%, 7-20wt%, 7-30wt%, 8-28wt%, 9-25wt%, 10-15wt%, 10-20wt%, 10-28wt%, 10-30wt%, 10-35wt%, 11-25wt%, 12-18wt%, 12-23wt%, 13-20wt%, 14-17wt%, 14-18wt%, 15-17wt% or any subranges or values ​​therebetween.

[0010] In some embodiments, the nanocellulose includes CNF, MFC, or its derivatives (e.g., modified CNF, modified MFC, e.g., carboxylated CNF) or any combination thereof. In some embodiments, the diameter of the nanocellulose is, for example, about 1-90nm, 1-80nm, 4-80nm, 5-70nm, 10-60nm, 15-50nm, 20-40nm, 25-30nm, 1-20nm, 4-10nm, 10-30nm, 20-80nm, or any sub-range or numerical value thereof. In some embodiments, the length of the nanocellulose is, for example, about or greater than 1 μm to less than 100 μm, for example, 1-95 μm, 1-3 μm, 1-10 μm, 15-30 μm, 5-20 μm, 1-20 μm, 20-30 μm, 20-50 μm, 30-70 μm, 30-80 μm, or any sub-range or numerical value thereof. 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 5-200, 15-150, 20-120, 30-100, 50-90, 100-2000, 150-1800, about 230-1500, about 500-1000, about 450-800, about 600-900, about 550-750, or any subrange or value therein.

[0011] In some embodiments, when formulating the composition, the nanocellulose is added in the form of a dispersion, wherein the weight ratio of the nanocellulose dispersion added to the sizing composition to the dry weight of the modified starch is about 1:100-500:100, such as about 5:100-500:100, such as 5:100-400:100, 10:100-50:100, 10:100-40:100. In some embodiments, the solid content of nanocellulose in the nanocellulose dispersion is about 0.5-10 wt%. In some embodiments, the weight ratio of the nanocellulose dispersion added to the composition to the dry weight of the modified starch added is about 5:100-500:100, such as about 5:100-450:100, 5:100-350:100, 5:100-250:100, 5:100-150:100, 10:100-400:100, 10:100-300:100, 10:100-200:100, 10:100-100:100, 10:100-50:100, 10:100-400:100, 10:100-350:100, 5:100-250:100, 5:100-150:100, 10:100-400:100, 10:100-300:100, 10:100-200:100, 10:100-100:100, 10:100-50:100, 10:100-300:100. 100, 35:100-50:100, 40:100-60:100, 50:100-90:100, or any sub-range or value therein.

[0012] 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, chemically modified MFC) and any combination thereof, wherein the diameter of the nanocellulose is about 1-80 nm. In some embodiments, when formulating the composition, the nanocellulose is added as a dispersion, and the weight ratio of the nanocellulose dispersion added to the modified starch dry weight added in the composition is about 10:100-100:100, for example, about 10:100-40:100. In some embodiments, the solid content of the nanocellulose in the nanocellulose dispersion is about 0.5-10 wt%.

[0013] In some embodiments, the solid content of nanocellulose in the nanocellulose dispersion is about 0.5-10wt%, such as about 0.5-5wt%, about 0.5-4.5wt%, about 0.6-4wt%, about 0.7-3wt%, about 0.8-3.5wt%, 1-2wt%, 1-2.5wt%, about 1-5wt%, about 1.5-7wt%, about 2-3wt%, about 2-5wt%, about 2.5-3.5wt%, about 2.5-6wt%, about 4-5wt%, about 5-9wt%, about 7-10wt%, about 8-10wt%, or any subrange or value therebetween.

[0014] In some embodiments, the sizing agent composition contains, consists of, or consists essentially of (a) modified starch; (b) nanocellulose; and (c) a medium, such as water.

[0015] In some embodiments, the sizing composition further comprises one or more other additives, such as preservatives, additional sizing agents, adhesives, fillers, coatings, waterproofing aids, dry strength agents, retention aids, etc., 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, etc. In some embodiments, the additional sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, AKD, SMA, EMA, PAC, wax emulsion, and rosin.

[0016] In some embodiments, the sizing agent composition contains, consists of, or consists essentially of (a) modified starch; (b) nanocellulose; (c) a medium (eg, an aqueous medium, such as water); and (d) a preservative.

[0017] In some embodiments, the sizing composition is a surface sizing composition.

[0018] In some embodiments, the sizing agent composition is in the form of a liquid (eg, a solution, a suspension, an emulsion). Therefore, in some embodiments, the sizing agent composition of the present invention is also referred to as a sizing liquid.

[0019] In some embodiments, the viscosity of the sizing solution is, for example, 5-1000 cps (according to the Brookfield ASTM standard method, tested at 65° C. using a No. 61, No. 62 or No. 63 rotor at a rotation speed of 30 rpm or 60 rpm). For example, the viscosity of the sizing solution is about 10-150cps, 10-200cps, 10-950cps, 10-1000cps, 30-90cps, 40-60cps, 40-70cps, 40-80cps, 50-75cps, 50-100cps, 50-150cps, 50-200cps, 50-500cps, 50-900cps, 100-850cps, 150-800cps, 200-750cps, 250-700cps, 300-650cps, 350-600cps, 400-500cps, or any sub-range or value therein.

[0020] The second aspect of the present invention provides an additive formulation for papermaking, which comprises 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: preservatives, additional sizing agents, adhesives, fillers, coatings, waterproofing aids, dry strength agents, retention aids, etc., such as silicone oil waterproofing agents, alkenyl succinic anhydride sizing agent compositions, AKD surface sizing agents, styrene acrylic emulsions, acrylic emulsions, SMA, etc. In some embodiments, the additive formulation also contains additional reinforcing aids, 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.

[0021] The third aspect of the present invention provides a method for using the sizing agent composition described in the first aspect of the present invention or the additive formulation described in the second aspect, comprising adding the sizing agent composition or the additive formulation into a paper machine system to coat the surface of paper.

[0022] In some embodiments, the size composition or additive formulation is applied by a paper dispenser.

[0023] In some embodiments, the method includes preheating the sizing composition or additive formulation to 45°C or higher (e.g., about 45-85°C, such as about 45°C-70°C, 55°C-65°C, 60°C-75°C, 65°C-80°C, 57°C, 59°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 82°C, or any range or value therebetween) and then applying it to the paper machine system. In some embodiments, the method includes controlling the paper machine sizing temperature at 45-85°C (e.g., about 50°C-80°C, 55°C-65°C, 60°C-65°C, 65°C-80°C, 57°C, 59°C, 62°C, 66°C, 67°C, 70°C, 72°C, 75°C, 78°C, 82°C, or any range or value therebetween) when applying the sizing composition or additive formulation.

[0024] In some embodiments, the sizing agent composition or additive formulation is applied to the paper surface by an automatic rod coater, a size press, a coating machine, or a calender.

[0025] The fourth aspect of the present invention provides a paper obtained using the sizing agent composition of the first aspect of the present invention or the additive formulation of the second aspect (eg, by the method of the third aspect).

[0026] The fifth aspect of the present invention provides a method for preparing the sizing agent composition described in the first aspect of the present invention, the method comprising: (1) preparing a modified starch solution; and (2) mixing a nanocellulose dispersion with the modified starch solution to prepare the sizing agent composition.

[0027] In some embodiments, step (1) comprises cooking the modified starch at 75-80° C. for 15-60 min (e.g., 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or any range, sub-range or value therebetween) to obtain a starch solution.

[0028] In some embodiments, when the modified starch is enzymatic starch, step (1) is (1'). In some embodiments, step (1') is completed using a three-step batch cooking method. For example, step (1') includes:

[0029] (1a) adding starch and amylase into water and cooking at 60-65°C for, e.g., 15-30 min (e.g., 15-20 min, 15-25 min, 20-25 min); (1b) raising the temperature to 75-80°C and cooking for, e.g., about 15-240 min (e.g., about 15-20 min, 20-150 min, 30-200 min, 50-250 min, 25-80 min or any subrange or value therebetween); (1c) raising the temperature to above 90°C (e.g., 92°C, 95°C, 98°C, 100°C or higher) to inactivate the amylase.

[0030] In some embodiments, in the mixture obtained in step (1a), the starch concentration can be about 5wt%-45wt% (for example, 5-28wt%, 6-27wt%, 7-25wt%, 8-23wt%, 9-22wt%, 10-19wt%, 10-20wt%, 10-35wt%, 10-42wt%, 11-16wt%, 11-20wt%, 10-28wt%, 11-40wt%, 12-18wt%, 12-30wt%, 13-14wt%, 13-32wt%, 15-17wt%, 15-38wt% or any range, sub-range or value therebetween). In some embodiments, in step (1a), the amount of amylase added is 20-150ppm (e.g., 20-140ppm, 25-135ppm, 30-130ppm, 50-120ppm, 60-100ppm, 70-90ppm or any range, subrange or value therebetween) of dry starch. In some embodiments, the amylase used in step (1a) is a medium temperature type amylase conventional in the art.

[0031] In some embodiments, in step (1c), the temperature is raised to above 90°C and then maintained for 20 minutes or longer (eg, 25 minutes, 30 minutes or longer).

[0032] In some embodiments, step (1') further comprises step (1d): cooling the starch solution prepared in step (1c) to room temperature. In some embodiments, step (1d) 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., 5-45 wt%). In some embodiments, step (1d) further comprises adding a preservative to the starch solution cooled to room temperature.

[0033] In some embodiments, when the modified starch is oxidized starch or cationic starch, step (1) is step (1"). In some embodiments, step (1") includes uniformly dispersing the oxidized starch or cationic starch in a medium (e.g., water) and heating. In some embodiments, the heating in step (1") includes heating to approximately 75-80°C and cooking for 30-40 min (e.g., 30 min, 32 min, 35 min, 38 min, 40 min, or any range, sub-range, or value therebetween) until the starch is completely gelatinized. In some embodiments, step (1") also includes cooling the gelatinized solution to room temperature to obtain a starch solution. In some embodiments, step (1") also includes 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., 5-45 wt%). In some embodiments, step (1") also includes adding a preservative to the cooled starch solution.

[0034] In some embodiments, the starch concentration of the starch solution obtained in step (1) is about 5-45wt% (e.g., 5-28wt%, 6-27wt%, 7-25wt%, 8-23wt%, 9-22wt%, 10-19wt%, 10-20wt%, 10-35wt%, 10-42wt%, 11-16wt%, 11-20wt%, 10-28wt%, 11-40wt%, 12-18wt%). %, 12-30wt%, 13-14wt%, 13-32wt%, 15-17wt%, 15-38wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 17wt%, 18wt%, 20wt%, 22wt%, 25wt%, 26wt%, 27wt%, 28wt%, 30wt%, 35wt%, 40wt% or any range, sub-range or value therebetween). In some embodiments, the viscosity of the starch solution obtained in step (1) is about 5-10000cps (e.g., about 10-9000cps, 50-8000cps, 100-7000cps, 150-6000cps, 200-5000cps, 250-4000cps, 300-3000cps, 350-2000cps, 400-1000cps, 150-7500cps, 250-5500cps, 350-4500cps, 450-3500cps, 550-2500cps, 650-1500cps, 750-1000cps, or any subrange or value therein).

[0035] In some embodiments, step (2) comprises mixing the nanocellulose dispersion (e.g., in any proportion) with the starch solution obtained in step (1) to form a nanocellulose / starch composite (which may be, for example, in the form of a suspension), i.e., the sizing agent composition of the first aspect of the invention.

[0036] In some embodiments, the solid content of the nanocellulose in the dispersion is about 0.5-10wt%, such as about 0.5-5wt%, about 0.5-4.5wt%, about 0.6-2wt%, about 0.7-4wt%, about 0.8-3wt%, about 0.9-3.5wt%, about 1-4.5wt%, about 1-2wt%, about 1-2.5wt%, about 1-5wt%, about 2-3wt%, about 2-5wt%, about 2.5-3.5wt%, about 2-6wt%, about 2.5-6wt%, about 3-7wt%, about 4-5wt%, about 4-8wt%, about 5-9wt%, about 5-10wt%, about 7-10wt%, about 8-10wt%, or any subrange or value therebetween.

[0037] The sixth aspect of the present invention provides use of the sizing agent composition or additive formulation as described above in papermaking.

[0038] Another aspect of the present invention also provides a kind of reagent bag, described reagent bag comprises the sizing agent composition described in each embodiment of the first aspect of the present invention or the additive formulation described in each embodiment of the second aspect and optional instructions for use.In some embodiments, described reagent bag also comprises preservative.In some embodiments, described modified starch and nano cellulose (for example nano cellulose dispersion) are separately packaged respectively.

[0039] In embodiments of the above various aspects, the nanocellulose dispersion is an aqueous nanocellulose dispersion.

[0040] In the embodiments of the various aspects described above, the paper machine suitable for use in the various aspects of the present invention is an eTAD paper machine or any other suitable paper machine known to those skilled in the art.

[0041] In embodiments of the above aspects, the additional or further sizing agent is selected from one or more of styrene acrylic emulsion, aluminum sulfate, AKD, SMA, EMA, PAC, wax emulsion and rosin.

[0042] In the embodiments of the above-mentioned various aspects, the sizing agent composition (or sizing solution) or additive formulation of the present invention can be used by the following methods: spraying, spraying, coating, applying, etc.

[0043] In the embodiments of the above aspects, the paper is common paper in the art, including but not limited to coated paper, white board paper, boxboard, kraft paper, packaging paper, corrugated paper, offset paper, ordinary cultural paper, drawing paper, cardboard or any combination thereof.

[0044] In the embodiments of the above aspects, the source of the modified starch includes but is not limited to corn starch, tapioca starch, and potato starch.

[0045] The sizing agent composition according to the present invention has the following advantages: it can significantly enhance the strength of paper and improve the properties of paper, such as improving the bursting index, ring crush index, printing performance, etc. of paper. In addition, the sizing agent composition of the present invention also has good stability, especially after adding a preservative, it can be stably stored for a long time (e.g., more than two months).

[0046] Other aspects and advantages of the present invention will become apparent to those skilled in the art from a reading of the ensuing description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above objects and features and other objects and features of the present invention will become apparent from the following description of the present invention in conjunction with the accompanying drawings, in which:

[0048] Figure 1 The effect of sizing agent compositions having different weight ratios of nanocellulose dispersion / starch dry weight on the bursting index according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0049] The scope of the present invention is not limited to any specific embodiments described herein.The following examples are offered for illustration only.

[0050] definition

[0051] The following definitions are provided to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

[0052] In the present invention, the term "optionally" means that the features (e.g., components, steps, etc.) defined by the term may or may not exist. For example, when referring to "optional instructions", it means that the instructions may or may not exist in the technical solution in question, and so on.

[0053] Cellulose nanocrystal (CNC) is a nanocellulose material with a diameter of about 1 to 20 nm and a length of about 100-800 nm (e.g., 100-500 nm, 200-800 nm). CNC is usually needle-shaped or rod-shaped and has a high degree of crystallinity. The aspect ratio of CNC is >5, for example, about 5-200, such as 5-150, 10-180, 20-170, 30-140, 50-100, 70-130 or any value or sub-range therebetween.

[0054] Cellulose nanofibrils (CNF) are nanocellulose materials with a diameter of about 4 to 80 nm (e.g., 4-10 nm, 10-30 nm, 20-80 nm) and a length of about 1-20 μm (e.g., about 1-3 μm, 1-10 μm, 1-20 μm). CNF is in the form of fibrils and is usually extracted from wood raw materials by physical methods such as grinding, high-pressure homogenization, etc. The aspect ratio of CNF is >100, for example, about 100-2000, such as 120-1800, 150-1500, 200-1300, 500-1000, 800-1400 or any value or sub-range therebetween.

[0055] Microfibrillated cellulose (MFC) is a nanocellulose material with a diameter of less than 100 nm and a length of more than 20 μm (for example, more than 30 μm). MFC refers to a disordered network composed of a large number of linear nanoscale microfibrils, and is a cellulose derivative.

[0056] 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.

[0057] In the present invention, when referring to "the weight ratio of the nanocellulose dispersion added to the sizing composition to the dry weight of the modified starch" or similar expressions, it refers to the weight ratio of the weight of the nanocellulose dispersion used to prepare the sizing composition of the present invention to the dry weight of the starch used to prepare the composition, unless otherwise specified.

[0058] In the present invention, when referring to "the weight ratio of the nanocellulose to the modified starch in the sizing composition" or similar expressions, it refers to the weight ratio of the weight of the nanocellulose itself used to prepare the sizing composition of the present invention to the dry weight of the starch used to prepare the composition, unless otherwise specified.

[0059] In the present invention, when it is mentioned that "the modified starch is present in the sizing 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.

[0060] In the present invention, when referring to "the modified starch and the nanocellulose are present in the sizing agent composition at 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.

[0061] In the present invention, when it is mentioned that "nanocellulose is present in the sizing composition in an amount of about z wt% by weight" or similar expressions, it can also mean that nanocellulose is present in the sizing composition in an amount of about z wt% based on solid content, which means that the weight of the nanocellulose itself used in the preparation of the composition accounts for about z wt% of the weight of the composition, unless otherwise specified.

[0062] In the present invention, "nanocellulose dispersion / modified starch dry weight ratio", "nanocellulose dispersion to modified starch dry weight ratio" or "nanocellulose dispersion / absolute dry starch weight ratio" or similar expressions can be used interchangeably.

[0063] In the present invention, "nanocellulose dispersion" refers to a nanocellulose slurry uniformly dispersed in water under a certain solid content condition.

[0064] In the present invention, unless otherwise defined, all other technical terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The percentages mentioned are weight percentages unless otherwise specified.

[0065] Nanocellulose, including CNF, MFC or CNC, is mainly produced from wood pulp. The lateral size of nanocellulose is usually 5-20nm, and the longitudinal size can reach hundreds of microns. During the manufacturing process, the pulp will be subjected to high shear forces, tearing the large wood fibers into nano-scale fibers. CNC has a very high stiffness (140-220GPa), comparable to Kevlar and even stronger than glass fiber, both of which can be used as reinforcing materials for plastic matrices. Thanks to the chemical properties of nanocellulose, its chemical structure is very similar to starch, and its surface has abundant hydroxyl groups. According to the inventor's discovery, nanocellulose can be used as a natural reinforcing additive for starch without the need for interfacial modification. This application proves that nanocellulose is an effective starch reinforcing additive and can therefore be used in combination with starch as a sizing agent composition, among which CNF and MFC or their derivatives (such as chemically modified CNF, chemically modified MFC) perform better.

[0066] In the present invention, nanocellulose dispersion is added to starch aqueous solution in an optimized ratio to form a sizing composition. The sizing composition is applied to various types of paper (including, for example, cardboard, drawing paper, and corrugated paper) to form a thin layer on the surface of the paper, thereby providing the paper with desired properties.

[0067] As demonstrated in the following examples, the inventors have found that the sizing agent composition of the present invention can significantly improve the bursting index, ring crush resistance index, etc. of the paper after sizing. At the same time, the sizing agent composition of the present invention can achieve a greater improvement in paper strength with a smaller coating amount relative to pure starch, which can potentially reduce the amount of dry strength agent added in the wet end and provide the possibility for lightweight papermaking.

[0068] In the sizing agent composition of the present invention, when nanocellulose (e.g., CNF, MFC, such as chemically modified CNF, chemically modified MFC) is mixed with starch in a higher ratio (e.g., the weight ratio of nanocellulose dispersion / starch dry weight is 100:100, 150:00, 200:100, 250:100, 300:100, 350:100, 400:100, 450:100, 500:100 or any range or value therebetween), an excellent reinforcement effect is also produced. For example, in the case of the above-mentioned nanocellulose dispersion / starch dry weight ratio, when the starch concentration in the sizing composition is about 10-25wt% (e.g., 10-20wt%) and is applied at a coating amount of about 40Kg / t, the sizing composition of the present invention is expected to produce an enhancement effect of about 5-15%; for example, the burst index is increased by about 5-15% (e.g., about 5-12%, 7-14%, 10-13%, 8%, 9%, 12%, 15% or any sub-range or value therebetween), or the ring crush index is increased by about 5-15% (e.g., about 5-12%, 7-14%, 10-13%, 8%, 9%, 12%, 15% or any sub-range or value therebetween), and / or the tensile index is increased by about 5-15% (e.g., about 5-12%, 7-14%, 10-13%, 8%, 9%, 12%, 15% or any sub-range or value therebetween).

[0069] It can be seen that the sizing agent composition of the present invention is very efficient and can be used in a sizing machine to enhance paper strength, improve retention, reduce air permeability, reduce paper roughness and improve paper printability, and has broad application prospects.

[0070] Example

[0071] The following examples further illustrate the technical solution of the present invention, but do not limit the protection scope of the present invention.

[0072] 1. The following components will be used in the examples:

[0073] (1) Nanocellulose

[0074] Table 1 lists the specific types and related parameters of nanocellulose (dispersion) used in the examples.

[0075] Table 1: Types of nanocellulose

[0076]

[0077] (2) Modified starch

[0078] Oxidized corn starch, for example, a 10% aqueous solution has a viscosity range of 10-100 cps at 65°C.

[0079] Enzymatically hydrolyzed corn starch (obtained by hydrolyzing native corn starch with amylase), for example, a 15% aqueous solution, with a viscosity range of 5-300 cps at 65°C.

[0080] 2. The properties of the sizing agent composition formulation prepared by the present invention and the paper properties are measured as follows:

[0081] (1) Burst index, measured according to TAPPI T-403 standard;

[0082] (2) Ring pressure index, measured according to TAPPI T-818 standard;

[0083] (3) tensile index, according to TAPPI T-494 standard;

[0084] (4) Viscosity: All viscosities were measured using a Brookfield viscometer, with a No. 2 or No. 3 spindle and a rotation speed of 30 rpm or 60 rpm;

[0085] (5) Solid content percentage: about 5 g of sample was placed in a 105 °C oven and dried, and then the dry-to-wet weight ratio was calculated to obtain the solid content percentage;

[0086] (6) Stability: Store the sample at room temperature and observe with the naked eye whether there is stratification, measure the change in viscosity, test the change in emulsion particle size, and take samples and dry them to test the change in solid content.

[0087] Example 1: Preparation of sizing agent composition

[0088] 1. Preparation of modified starch solution

[0089] (1) Enzymatic starch solution

[0090] Add 50-150ppm amylase to corn starch and cook at 60-65℃ for 15-60 minutes. Then heat to above 95℃ for high temperature inactivation. The concentration of the enzymatic starch solution is finally controlled at 10-40wt%, and the viscosity range is 5-10000cps. Table 2 below shows various enzymatic starch solutions prepared in this example.

[0091] Table 2: Enzymatic starch solution

[0092]

[0093] (2) Oxidized starch solution

[0094] Corn starch is cooked at 80°C for 20 minutes to obtain a uniform starch solution. For example, the concentration of oxidized starch is 10 wt%, and the viscosity is 30 cps at 65°C.

[0095] 2. Preparation of sizing agent composition

[0096] The nanocellulose dispersion of Table 1 was mixed with the starch solution obtained above in different proportions to obtain a sizing composition formula (i.e., sizing solution) containing different starch and nanocellulose concentrations. When used, the sizing solution can be heated to 55-75° C. Table 3-1 shows some examples of sizing composition formulas prepared by the present invention and related parameters, wherein the cellulose is CNF-1 and the starch is enzymatic starch.

[0097] Table 3-1: Sizing agent composition formula

[0098]

[0099] 3. Stability of sizing agent composition

[0100] The sizing 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 performance indicators (such as viscosity, emulsion particle size, solid content). The results showed that the sizing composition of the present invention had excellent stability, as shown in Tables 3-2 and 3-3 below (wherein Table 3-2 used oxidized starch, and Table 3-3 used enzymatic starch).

[0101] Table 3-2: Stability of sizing agent composition formula

[0102]

[0103] Table 3-3: Stability of sizing agent composition formula

[0104]

[0105] Example 2: Effects of different nanocellulose types on paper properties

[0106] Using the method described in Example 1, different sizing agent composition formulations were prepared using enzymatically hydrolyzed corn starch and various nanocellulose dispersions in Table 1, with a cellulose dispersion / absolutely dry starch weight ratio of 10:100 and a starch solid content of 15%. Pure enzymatically hydrolyzed starch (without nanocellulose) was used as a blank control.

[0107] The prepared formulation was coated on kraft paper at a coating amount of 40 kg / ton, and the effect on paper properties was measured. The results are shown in Table 4 below.

[0108] Table 4: Effects of different nanocelluloses on paper properties

[0109]

[0110] It can be seen from Table 4 that compared with CNC, CNF and MFC are more suitable for compounding with enzymatic starch solution, and can be stored stably for a long time after adding appropriate amount of preservatives. However, CNC is prone to instability after mixing with starch solution.

[0111] Example 3: Effect of Nanocellulose Dispersion / Modified Starch Dry Weight Ratio on Paper Properties

[0112] Using the method described in Example 1, different sizing agent composition formulations were prepared using enzymatically hydrolyzed corn starch and nanocellulose CNF-2 at a cellulose dispersion / starch dry weight weight ratio of 5:100, 10:100, 15:100, 20:100, 30:100, 40:100, 50:100, and 600:100 (high concentration). Enzymatically hydrolyzed corn starch (without nanocellulose) was used as a blank control.

[0113] The prepared formula was coated on corrugated paper and the effect on paper properties was measured. The results are shown in Table 5-1 below.

[0114] Table 5-1: Effect of nanocellulose dispersion / modified starch dry weight ratio on paper properties

[0115]

[0116] It can be seen from the experimental results that when the nanocellulose dispersion / starch dry weight ratio reaches only 5:100, an obvious improvement effect appears. For nanocellulose of different types and sizes, the appropriate weight ratio is in the range of 5:100-50:100, and the optimal range is between 10:100-40:100 and 20:100-40:100. The coated paper has excellent physical strength. When the nanocellulose dispersion / starch dry weight ratio exceeds 50:100, it also has an enhancement effect on the paper, and the performance can be improved by 5-15%. The inventors found that as the concentration of nanocellulose increases, flocculation will form in the starch solution, and larger cellulose flocs will block the gaps in the paper, hindering the sizing solution from penetrating into the interior of the paper, affecting its enhancement effect.

[0117] In addition, the method described in Example 1 was used to prepare sizing agent composition formulas with different cellulose dispersion / starch dry weight ratios (5:100, 10:100, 20:100, 30:100, 40:100) using enzymatically hydrolyzed corn starch (Table 5-2, solid content: 14-15wt%), oxidized cassava starch (Table 5-3, solid content: 11-12wt%), oxidized corn starch (Table 5-4, 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.

[0118] The prepared formula was coated on corrugated paper or kraft paper, and the effect on the bursting index was measured. The results are shown in Table 5-2, Table 5-3 and Table 5-4 below.

[0119] Table 5-2: Effect of different dry weight ratios on the bursting index of kraft paper

[0120]

[0121] According to Table 5-2, different dosage ratios of nanocellulose: modified starch have significantly better performance than unmodified starch and dry strength agent added in the wet end. Figure 1 middle.

[0122] Table 5-3: Effect of sizing agent composition formula on corrugated paper performance

[0123]

[0124] Table 5-4: Effect of sizing agent composition formula on kraft paper properties

[0125]

[0126] It can be seen from Table 5-3 and Table 5-4 that CNF produces better performance when applied to both corrugated paper and kraft paper, and has a significant improvement in the tear resistance of both kraft paper and corrugated paper.

[0127] Example 4: Sizing agent composition formulation and performance of the present invention

[0128] Using the method described in Example 1, different sizing agent composition formulas were prepared using enzymatically hydrolyzed corn starch and different types of nanocellulose at a cellulose dispersion / starch dry weight ratio of 1:100, 5:100, 10:100, 15:100, 20:100, 30:100, and 50:100, respectively. The prepared sizing agent composition formulas are shown in Table 6 below.

[0129]

[0130] The prepared formulation was coated on kraft paper, and the properties of the coated paper were measured. The results are shown in Table 7 below.

[0131] Table 7: Effect of sizing agent composition formulation on paper properties

[0132]

[0133] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present 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 present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A sizing agent composition for papermaking, comprising: (a) modified starch; and (b) nanocellulose, The nanocellulose has a diameter of about 1-100 nm and a length of about 1 μm or more, and Optionally, the weight ratio of the nanocellulose to the modified starch in the sizing agent composition is about 0.005:100-60:100, such as about 0.01:100-50:100, 0.015:100-45:100, 0.2:100-5:100, 0.3:100-3:

100.

2. The sizing composition according to claim 1, wherein the modified starch is present in the sizing composition in an amount of about 5-30 wt% by weight, such as 10-20 wt%, 14-18 wt%, and / or wherein the nanocellulose is present in the sizing composition in an amount of about 0.005 wt%-3 wt%, such as 0.01 wt%-1 wt%, 0.01 wt%-0.3 wt% by weight.

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, and / or wherein the modified starch comprises oxidized starch, enzymatic starch, cationic starch or any combination thereof, Optionally, the modified starch and the nanocellulose are present in the sizing agent composition in an amount of about 5-40 wt%, such as 10-35 wt%, 7-20 wt%, by weight.

4. The sizing agent composition according to any one of claims 1 to 3, wherein the length of the nanocellulose is greater than or equal to about 1 μm and less than about 100 μm, Optionally, wherein the diameter of the nanocellulose is about 1-80 nm, and Optionally, the sizing agent composition further comprises one or more other adjuvants selected from: preservatives, additional sizing agents, adhesives, fillers, coatings, waterproofing aids, dry strength agents, retention aids or any combination thereof.

5. The sizing composition according to any one of claims 1 to 4, wherein the sizing composition is used for surface sizing, and optionally, the sizing composition has a viscosity of about 5-1000 cps, such as 50-500 cps, when tested at 65° C. and 30 rpm using a No. 62 rotor according to the Brookfield ASTM standard method.

6. The papermaking sizing agent composition according to any one of claims 1 to 5, wherein when preparing the composition, the nanocellulose is added in the form of a dispersion, wherein the weight ratio of the nanocellulose dispersion added to the sizing agent composition to the dry weight of the modified starch is about 1:100-500:100, such as about 5:100-500:100, 5:100-400:100, 10:100-50:100, 10:100-40:100, Optionally, the solid content of nanocellulose in the nanocellulose dispersion is about 0.5-10 wt %, such as about 1-5 wt % or 7-10 wt %.

7. A papermaking additive formulation comprising the sizing agent composition according to any one of claims 1 to 6 and one or more additional additives, Optionally, wherein the one or more additional additives are selected from: preservatives, additional sizing agents, adhesives, fillers, coatings, waterproofing aids, dry strength agents, retention aids, or any combination thereof.

8. The sizing composition according to claim 5 or the additive formulation 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 in a papermaking process using the sizing composition of any one of claims 1 to 6 and 8 or the additive formulation of any one of claims 7 to 8, comprising applying the sizing composition or additive formulation to a paper surface, optionally by an automatic rod coater, a size press, a coating machine, a calender or any combination thereof.

10. The method of claim 9, further comprising heating the size composition or additive formulation to about 45°C-85°C prior to application, and optionally controlling the paper machine sizing temperature at about 45-85°C when applying the size composition or additive formulation.

11. Paper obtainable 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 to 6 and 8, comprising: (1) providing a modified starch solution (e.g., having a viscosity of about 5-10,000 cps and a modified starch concentration of about 5-45 wt %); and (2) mixing the nanocellulose dispersion with the modified starch solution to prepare the sizing agent composition, Optionally, the solid content of the nanocellulose in the dispersion is about 0.5-10 wt %.

13. The method according to claim 12, wherein step (1) comprises cooling the prepared modified starch solution to room temperature and adding a preservative, Optionally, step (1) further comprises adding about 20-150 ppm of amylase to the prepared modified starch solution based on the weight of the dry modified starch.

14. The sizing composition according to any one of claims 1-6, 8, the additive formulation according to any one of claims 7-8, or the method according to any one of claims 9-10, 12-13, wherein the sizing composition or the additive formulation is suitable for paper selected from the following: coated paper, white board, boxboard, kraft paper, wrapping paper, corrugated paper, offset paper, ordinary cultural paper, drawing, paperboard or any combination thereof; or the paper according to claim 11, wherein the paper is selected from: coated paper, white board, boxboard, kraft paper, wrapping paper, corrugated paper, offset paper, ordinary cultural paper, drawing, paperboard or any combination thereof.

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