Double emulsification of alkenyl succinic anhydride to improve sizing performance and stability

Abstract

The present invention relates to compositions and methods for preparing stable alkenyl succinic anhydride (ASA) sizing emulsions, which potentially can be used in the manufacture of paper and paperboard. In particular, the present disclosure provides methods for double emulsification of ASA using a cationic polymer as a primary emulsifier and a cationic starch as a secondary emulsifier that significantly reduce total starch utilization compared to conventional natural polymer ASA emulsification applications. The invention also relates to methods for producing high ash paper and paperboard using these ASA sizing emulsions.

Description

[0001] Related applications

[0002] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 456,265, filed March 31, 2023, and Finnish Application No. 20236040, filed September 20, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] This invention generally relates to compositions and methods for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard. In particular, this disclosure provides a method for co-emulsifying ASA using a cationic polymer as a primary emulsifier and cationic starch as a secondary emulsifier, which imparts excellent stability to the emulsion with a significantly reduced total starch utilization rate and enhances the sizing performance of woodless papermaking systems that typically contain high ash content, compared to conventional natural polymer ASA emulsification applications. Background Technology

[0004] In the papermaking and finishing processes, sizing agents are commonly used to provide the desired properties of the final paper product. Sizing, or sizing properties, are a measure of the resistance of the resulting paper or paperboard product to penetration or wetting by aqueous liquids, water, or inks.

[0005] Sizing agents are typically internal additives used during papermaking to increase this resistance, or external surface additives used on finished sheets or webs. Sizing agents can be a variety of substances used to promote liquid resistance, including but not limited to water, ink, or other media, to protect the paper surface. These substances are generally used to prevent fluids from being absorbed by the paper.

[0006] Alkenyl succinic anhydride (ASA) is a commonly used internal sizing agent in papermaking. ASA sizing agents are often hydrophobic and usually must be used in water-based papermaking systems.

[0007] ASA is typically emulsified in a natural polymer (usually modified cationic starch) or a synthetic cationic polymer and then introduced into the wet end of the paper machine. Because ASA emulsions made using natural or synthetic polymers are unstable, they are usually produced on-site at the plant using equipment that provides sufficient shear to produce an effective emulsion for direct application to the machine or application within a few hours of manufacturing. While the use of (high) starch during ASA emulsification offers significant benefits for emulsion quality, sizing retention, and overall sizing efficiency, the extensive use of starch at the wet end of the papermaking process increases web water retention with increasing starch content, and conversely, decreases web water retention with decreasing wet-end starch content. Higher water retention reduces web press efficiency, thereby reducing the solids content of the web leaving the press. This increases the drying energy requirements of the sheet and can potentially reduce productivity and overall paper machine runnability.

[0008] Obtaining a uniform and stable ASA emulsion suitable for papermaking requires considerable effort. The hydrochemistry of the process and various pulping components can adversely affect the efficiency of ASA sizing. Therefore, in alkaline printing and writing grades, and some packaging grades (where calcium carbonate and various kaolin pigments are used), where high ash content is often observed, the efficiency of applying synthetic polymer-emulsified ASA alone, or when a large amount of free calcium ions is present at the wet end, is generally impractical. Typically, [Ca++] >150 ppm as calcium or 400 ppm as calcium carbonate is considered high.

[0009] Currently, the availability of starch for commercial applications is severely limited due to supply chain shortages. This invention seeks to utilize a dual-emulsification technology, employing a cationic solution polymer in the primary emulsification step, followed by secondary emulsification of the starch at a low dose under shear. This invention also seeks to form low-starch ASA sizing emulsions suitable for high-ash pulps, for the preparation of ink-resistant and water-resistant writing and printing grade paper and paperboard. Compared to conventional natural polymer ASA emulsification applications, dual-emulsification imparts superior stability to the emulsion with a significantly reduced total starch utilization rate and improves sizing performance in high-ash papermaking. Summary of the Invention

[0010] This invention generally relates to compositions and methods for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard. In particular, this disclosure provides a method for co-emulsifying ASA using a cationic polymer as a primary emulsifier and cationic starch as a secondary emulsifier, which imparts excellent stability to the emulsion and enhances sizing performance in high-ash papermaking with a significantly reduced total starch utilization rate compared to conventional natural polymer ASA emulsification applications.

[0011] On one hand, the present invention provides a method for preparing a stable alkenyl succinic anhydride (ASA) sizing emulsion suitable for manufacturing paper and paperboard, the method comprising:

[0012] (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent;

[0013] (b) Combining and emulsifying the ASA sizing agent with a primary emulsifier to form a primary emulsion; and

[0014] (c) Following step (b), a secondary emulsifier is added and emulsified to form the ASA sizing emulsion, and

[0015] (d) Optionally, after steps (a) to (c), the resulting stable ASA sizing emulsion is added to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp.

[0016] In some exemplary embodiments, the method further includes, after step (c):

[0017] (a) Adding the ASA sizing emulsion to the papermaking pulp, pulp, or fiber raw material; or

[0018] (b) Add the ASA sizing emulsion to the high ash content slurry, the high ash content slurry comprising ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof, wherein the high ash content slurry comprises 1-35%, 2-30%, 5-25%, or 10-20% ash content by weight, preferably 5%-25% ash by weight.

[0019] In some exemplary embodiments, the ASA sizing agent comprises:

[0020] (a) ASA solid, ASA waxy solid, ASA waxy liquid, ASA liquid, or mixtures thereof; and

[0021] (b) A single ASA sizing agent or a mixture of ASA sizing agent molecules and / or isomers.

[0022] In some exemplary embodiments of the method, (i) the primary emulsifier comprises an aqueous polymer solution containing one or more cationic polymers and water; and (ii) the secondary emulsifier comprises one or more cationic starches.

[0023] In some exemplary embodiments, the polymer aqueous solution comprises one or more cationic polymers in the range of 1-70%, 2-50%, or 5-30% by solid weight.

[0024] In some exemplary embodiments, the one or more cationic polymers comprise:

[0025] (a) One or more synthetic copolymers, terpolymers, or quaternaries comprising acrylamide and one or more cationic monomers, wherein the one or more cationic monomers are selected from the group consisting of:

[0026] (i) diallyl dialkyl ammonium halides, including but not limited to diallyl dimethyl ammonium chloride (“DADMAC”) and diallyl diethyl ammonium chloride;

[0027] (ii) N,N-dialkylaminoalkyl acrylates, (meth)acrylates, and their acid addition salts and / or quaternary ammonium salts, including but not limited to acryloyloxyethyltrimethylammonium chloride (“AETAC”), methacryloyloxyethyltrimethylammonium chloride (“MAETAC”), dimethylaminoethyl acrylate (“DMAEA”) and its acid addition salts, dimethylaminoethyl methacrylate (“DMAEMA”) and its acid addition salts, dimethylaminoethyl acrylate methyl sulfate quaternary ammonium salt, dimethylaminoethyl acrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl acrylate sulfate, dimethylaminoethyl acrylate hydrochloride, diethylaminoethyl acrylate, methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate sulfate, dimethylaminoethyl methacrylate hydrochloride, dimethylaminoethyl methacryloyl hydrochloride;

[0028] (iii) N,N-dialkylaminoalkylacrylamides and N,N-dialkylaminoalkyl(methyl)acrylamides and their acid addition salts or quaternary ammonium salts, including but not limited to acrylamidopropyltrimethylammonium chloride (“APTAC”), methacrylamidopropyltrimethylammonium chloride (“MAPTAC”), dimethylaminopropylacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylacrylamide sulfate, dimethylaminopropylacrylamide hydrochloride, dimethylaminopropylmethacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylmethacrylamide sulfate, dimethylaminopropylmethacrylamide hydrochloride, diethylaminoethyl acrylate, diethylaminoethyl methacrylate; or

[0029] Any combination of (iv)(i)-(iii);

[0030] (b)(a) one or more synthetic copolymers, terpolymers or quaternaries, wherein the one or more synthetic copolymers, terpolymers or quaternaries optionally contain:

[0031] (i) one or more other nonionic monomers selected from the group consisting of: methacrylamide; N-alkylacrylamide, including but not limited to N-methacrylamide, N-ethylacrylamide, N-propylacrylamide and N-butylacrylamide; N,N-dialkylacrylamide, including but not limited to N,N-dimethylacrylamide and N,N-diethylacrylamide; N-alkylmethylacrylamide; alkyl acrylate; hydroxyalkyl acrylate and hydroxyalkyl methacrylate, including but not limited to methyl acrylate, 2-hydroxyethyl acrylate and 3-hydroxypropyl acrylate. 4-Hydroxybutyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate; dialkyl acrylates and dialkyl methacrylates, including but not limited to 2,3-dihydroxypropyl acrylate, 3,4-dihydroxybutyl acrylate, 2,3-dihydroxypropyl methacrylate (DHPMA), and 3,4-dihydroxybutyl methacrylate; alkyl acrylates, including but not limited to methyl methacrylate; acrylonitrile; N-vinylmethylacetamide, N-vinylmethylformamide; N-vinyl acetate, glyoxalated acrylamide, and vinylpyrrolidone;

[0032] (ii) One or more additional anionic monomers selected from the group consisting of: acrylic acid, methacrylic acid, sulfonic acid, phosphonic acid, and their alkali metal salts, alkaline earth metal salts, and ammonium salts, including but not limited to acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamidomethanesulfonic acid, acrylamidoethanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid; or

[0033] Any combination of (iii)(i)-(ii);

[0034] (c) One or more cationic glyoxalized polyacrylamide (GPAM) polymers, said one or more cationic GPAM polymers being obtained by reacting glyoxal with one or more synthetic copolymers, terpolymers or quaternary copolymers of (a), one or more synthetic copolymers, terpolymers or quaternary copolymers of (b), or combinations thereof;

[0035] (d) One or more semi-synthetic polymers comprising (a) or (b) the one or more synthetic copolymers, terpolymers, or quaternary copolymers optionally grafted onto one or more natural polymers, including but not limited to starch, chitin, chitosan, and natural polysaccharides; or

[0036] (e)(a) to (d) any combination

[0037] And the one or more cationic polymers said therein have a weight-average molecular weight in the range of 10,000-3,000,000 Da, 10,000-2,000,000 Da, 10,000-1,000,000 Da, 10,000-500,000 Da, 10,000-200,000 Da, 10,000-100,000 Da or 10,000-50,000 Da.

[0038] In some exemplary embodiments, the one or more cationic starches:

[0039] (a) A cationic modified or unmodified starch comprising one or more of the following groups: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, rice starch, barley starch, pea starch, sweet potato starch, and any combination thereof; and

[0040] (b) having a nitrogen content percentage (N%) ranging from 0.2-2%, 0.2-1.75%, 0.2-1.5%, 0.2-1.25%, 0.2-1% or 0.25-0.45% by mass, preferably 0.35-1.45% by mass.

[0041] In some exemplary embodiments, the one or more cationic starches are formulated by a method comprising the following steps before being added to the ASA sizing agent:

[0042] (a) Dissolving dry cationic starch in water; cooking by methods including but not limited to spray cooking, steam cooking, or pot cooking; and cooling to a temperature in the range of 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, to obtain a cooked starch solution with a solid percentage in the range of 1-10%, 2-8%, or 3-6% by mass; or

[0043] (b) Obtain a pregelatinized cationic starch with a solid percentage ranging from 20% to 40% by mass, and dilute it with water to obtain a pregelatinized starch solution with a solid percentage ranging from 1-10%, 2-8%, or 3-6% by mass.

[0044] In some exemplary embodiments of the method, (i) the one or more cationic polymers are selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) quaternary copolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer, and (ii) the one or more cationic starches comprise corn starch, waxy corn starch, potato starch, cassava starch, wheat starch, or pea starch.

[0045] In some exemplary embodiments, the method includes one or more of the following:

[0046] (a) Adding the primary emulsifier to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and

[0047] (b) The secondary emulsifier is added to the primary emulsion to obtain a dry starch to ASA mass ratio of 0.25:1 to 2:1, 0.3:1 to 1.6:1, 0.4:1 to 1.2:1 or 0.5:1 to 1:1.

[0048] In some exemplary embodiments, the method includes:

[0049] (a) The primary emulsifier is added to the ASA sizing agent at ambient temperature and emulsified by stirring with an energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm or 0.5-1 μm;

[0050] (b) The secondary emulsifier is added to the primary emulsion at a temperature in the range of 20-80°C, 20-60°C, 20-40°C or 20-25°C, preferably 20-40°C, and emulsification is carried out by stirring with energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm or 0.5-1 μm.

[0051] In some exemplary embodiments, the ASA sizing emulsion in its final form is as follows:

[0052] (a) Includes median particle sizes with diameters ranging from 0.5–1 μm, 0.6–0.9 μm, or 0.7–0.8 μm;

[0053] (b) Viscosities ranging from 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP, or 50-60 cP when measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C.

[0054] (c) It exhibits stability over 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours, or 1-48 hours, wherein the stability is determined by the ASA sizing emulsion, and the ASA sizing emulsion retains...

[0055] (1) A median particle size with a diameter of 0.5-3 μm, 0.5-2 μm, 0.5-1 μm, 0.6-0.9 μm or 0.7-0.8 μm, preferably less than 1 μm; and / or

[0056] (2) When measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C, the viscosity range is 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP or 50-60 cP, preferably less than 100 cP.

[0057] (d) Add immediately to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp, or store in a tank or holding facility for 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours or 1-48 hours before adding the ASA sizing emulsion to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp;

[0058] (e) Compared to ASA sizing emulsions prepared by a single or dual emulsification method using one or more emulsifiers containing one or more cationic starches, it contains a reduced final mass ratio of dry starch to ASA; or

[0059] Any combination of (f)(a)-(e).

[0060] In some exemplary embodiments, when the stabilized alkenyl succinic anhydride (ASA) sizing emulsion is used as a sizing agent during the manufacture of the paper or paperboard, it produces sheet products selected from the group consisting of: high ash paper or paperboard, printing or writing grade paper or paperboard, alkaline printing or writing grade paper or paperboard, bleached paper or paperboard, packaging grade paper or paperboard, and partially recycled or 100% recycled paper or paperboard, wherein the sheet products contain optimal sizing performance as determined by industry-standardized testing, including but not limited to HST, Cobb, water droplet test, contact angle, edge wicking, or water permeability, wherein the optimal sizing performance is determined relative to an equivalent sheet product comprising an ASA sizing emulsion prepared by a monoemulsification or doubulsification method using one or more emulsifiers containing one or more cationic starches.

[0061] On the other hand, the present invention provides a dual emulsification method for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard, the method comprising:

[0062] (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent;

[0063] (b) The ASA sizing agent is combined with a primary emulsifier and emulsified at ambient temperature, and stirred with energy sufficient to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming a primary emulsion; and

[0064] (c) Following step (b), a secondary emulsifier is added and emulsified at a temperature ranging from 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, and stirred with sufficient energy to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming the ASA sizing emulsion, and

[0065] (d) Optionally, after step (c), the ASA sizing emulsion is added to the high-ash paper pulp, wherein

[0066] (i) The primary emulsifier comprises an aqueous polymer solution containing an acrylamide cationic copolymer selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) tetropolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer;

[0067] (ii) The secondary emulsifier comprises one or more cationic modified or unmodified starches selected from the group consisting of: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, pea starch, and mixtures thereof;

[0068] (iii) The high-ash paper pulp comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof;

[0069] (iv) The high-ash pulp contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5-25% ash by weight;

[0070] (v) The primary emulsifier is added to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and

[0071] (vi) The secondary emulsifier is added to the primary emulsion to obtain a dry starch to ASA mass ratio of 0.25:1 to 2:1, 0.3:1 to 1.6:1, 0.4:1 to 1.2:1 or 0.5:1 to 1:1.

[0072] On the other hand, the present invention provides an ASA sizing emulsion composition or a papermaking pulp, pulp or fiber raw material comprising the ASA sizing emulsion composition, optionally a high ash pulp, wherein the ASA sizing emulsion composition or papermaking pulp, pulp or fiber raw material can be obtained by the method according to any one of the foregoing.

[0073] On the other hand, the present invention provides a method for producing paper or paperboard, the method comprising obtaining a high ash distribution pulp comprising wood pulp, optionally comprising a fiber raw material comprising a high content of recycled fiber and / or factory waste paper fiber, optionally a coarse fiber raw material, optionally a bleached fiber raw material, optionally containing process water from pulp, paper or paperboard production; and treating the fiber raw material at the wet end of a paper machine with an ASA sizing emulsion according to any one of the preceding claims, wherein:

[0074] (a) The high-ash slurry comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof; and

[0075] (b) The high ash content slurry contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5%-25% by weight. Attached Figure Description

[0076] The present invention will now be described in more detail with reference to the accompanying drawings.

[0077] Figure 1 Exemplary flowcharts are provided for a conventional emulsification method (conventional) for ASA according to Example 1 and a dual emulsification method (new two-step method) of the present invention.

[0078] Figure 2 An exemplary table showing the results of measurements of the composition, particle size, and viscosity of the primary, secondary, and control ASA emulsions according to Example 1 is provided.

[0079] Figure 3 An exemplary variation graph of Cobb values ​​according to Example 2 is shown, indicating the water absorption of handmade paper prepared with the dual-emulsified ASA sizing emulsion of the present invention and the control ASA sizing emulsion.

[0080] Figure 4 An exemplary variation graph of the Hercules size test (HST) according to Example 2 is shown, indicating the amount of ink penetrating into handmade paper prepared with the dual-emulsified ASA sizing emulsion of the present invention and the control ASA sizing emulsion.

[0081] Figure 5 An exemplary bar graph of HST values ​​according to Example 3 is shown, indicating the shortcomings when starch alone or synthetic polymer alone is used as an emulsifier for ASA sizing emulsions used for high ash paper pulp sizing.

[0082] Figure 6An exemplary bar graph of Cobb values ​​according to Example 3 is shown, indicating that the ASA emulsion prepared using the dual emulsification method of the present invention (red bar) has similar sizing properties compared to starch alone (blue bar). Detailed Implementation

[0083] Before describing the present invention, the following definitions are provided. Unless otherwise stated, all terms should be interpreted in accordance with the understanding of those skilled in the art.

[0084] definition

[0085] As used herein, the singular forms “a,” “and,” and “the” include the plural reference unless the context clearly specifies otherwise.

[0086] As used herein, the terms “N content percentage” and “N content %” refer to the molar percentage of nitrogen substitution in cationic starch.

[0087] As used in this article, the term "retention" refers to the efficiency with which small particles or chemical additives are retained in the paper during paper formation, rather than along with the white water.

[0088] As used herein, the terms "papermaking process" and "papermaking application" generally refer to any process capable of producing paper and / or paperboard articles of any form. Such processes include, for example, the manufacture of paper articles from pulp, including methods comprising forming an aqueous cellulose papermaking pulp, draining the pulp to form paper, and drying the paper. The steps of forming the papermaking pulp, draining, and drying can be performed in any conventional manner known in the art. In some cases, papermaking processes and applications may involve the use of one or more sizing agents added to the papermaking pulp.

[0089] As used in this article, the term "fiber" refers to the basic structural unit of paper or paperboard.

[0090] As used herein, the terms “recycled fiber” and “reclaimed fiber” refer to paper, paperboard, and fiber waste from retail stores, office buildings, residences, manufacturing plants, etc., after they have been used as consumer products. Manufacturing waste includes: dry paper and paperboard waste generated after the completion of papermaking processes, such as envelope scraps, binding trimmings, and other paper and paperboard waste generated from printing, cutting, forming, and other processing operations; bag, box, and carton manufacturing waste; factory packaging paper and unused raw materials; and finished paper and paperboard repulped from obsolete stockpiles of paper and paperboard manufacturers, merchants, wholesalers, distributors, printers, processors, or other parties. Specifically, the term “recycled fiber” includes recycled fibers obtained through processing paper and other consumer cellulosic materials, such as paper, old corrugated cardboard (OCC), mixed office waste (MOW), old magazines (OMG), unbleached kraft pulp, neutral sulfite semi-chemical (NCCS) pulp, and / or mechanical pulp. Raw materials for recycled fibers can be selected from used corrugated cardboard, mixed office waste, used newsprint, used magazines, double-lined kraft paper, and any mixture thereof. Mixed waste (MXW) refers to a recycled mixture of recycled paperboard (such as OCC, white paperboard, and / or folding linerboard) and recycled paper (such as used newsprint, used magazines, and / or office waste). Mixed office waste refers to recycled fiber materials primarily consisting of copy paper, printer paper, and offset paper. Double-lined kraft paper refers to recycled fiber materials containing clean, sorted, unprinted corrugated cardboard boxes, cartons, paper, or scraps (such as kraft paper or jute lining). White paperboard (WLC) refers to multi-layer paperboard in which one or more layers contain deinked fiber materials and / or undeinked recycled fiber materials derived from, for example, OCC, mixed office waste, or used newspapers (ONP). The presence of any of these recycled fiber materials in the fiber suspension typically reduces drainage and paper strength, and provides the process with a significant amount of starch, hydrophobic, and colloidal substances.

[0091] As used herein, the term "OCC" refers to recycled corrugated cardboard and / or boxboard. Corrugated boxes are those made of three separate layers of paper, two layers of linerboard, and a corrugated or wave-shaped layer sandwiched between them. Brown paper bags are often accepted for recycling along with OCC. The term OCC indicates recycled fiber material with linerboards such as test linerboard, jute, or kraft paper, and may also include double-sorted recycled corrugated boxboard (DSOCC).

[0092] As used herein, the term "waste paper" or "factory waste paper" refers to paper that becomes only suitable for repulping during the papermaking process, such as scraps or non-standard paper. Waste paper is reused material that never leaves the factory and is not considered recycled or recycled. Waste paper is a valuable source of fiber that can be recycled within the factory.

[0093] As used herein, the term "fiber suspension" should be understood as an aqueous suspension comprising fibers (preferably recycled fibers) and optionally fillers. For example, for wood-free communication paper and specialty paper, the fiber suspension may contain at least 5%, 10-30%, or 11-19% by weight of mineral fillers, preferably 5%-25%. The mineral fillers may be any fillers conventionally used in paper and paperboard manufacturing, such as ground calcium carbonate, precipitated calcium carbonate, clay, talc, gypsum, titanium dioxide, synthetic silicates, aluminum trihydrate, barium sulfate, magnesium oxide, or any mixture thereof.

[0094] As used herein, the term “pulp formulation” or “paper pulp formulation” generally refers to a mixture of cellulose fibers, pulp, optional fillers, dyes and water used to make paper or paperboard.

[0095] As used herein, the term "thick pulp" generally refers to a mixture of paper pulp and other materials with a consistency of about 1% to 5%.

[0096] As used herein, the term "slurry" generally refers to a mixture of paper pulp and other materials in a sector pump after it has been diluted with white water or other process water to a consistency of less than 1%.

[0097] As used herein, the term "high ash content pulp" refers to a pulp containing ash components, including but not limited to calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof. High ash content paper pulps are considered to contain 1-35%, 2-30%, 5-25%, or 10-20% ash content by weight, preferably 5%-25% by weight for woodfree communication paper and specialty paper. Such pulps are commonly used in papermaking applications to produce alkaline writing or printing grade paper and packaging materials.

[0098] As used herein, the term "sizing agent" generally refers to various substances used to promote water and water resistance on the surface of materials such as paper, cardboard, textiles, or composites, and is typically hydrophobic. These substances are usually used to prevent liquids from being absorbed by the paper.

[0099] As used herein, the terms “sizing performance” or “optimal sizing performance” can be determined through industry-standardized tests, including but not limited to: HST, Cobb, water droplet test, contact angle, edge wicking, or water penetration. Neither HST nor Cobb is specifically designed for ink and water resistance, respectively. Both tests are used based on the sizing level required for the end-use. Sizing requirements for (office) printing paper are not stringent, so the HST test is often well-suited and more automated. For higher sizing requirements, Cobb is typically used, and runs can last 1 or 2 minutes, but for some packaging grades, up to 30 minutes. Other sizing tests, such as water droplet, edge wicking, ink float, and contact angle, can also be utilized. The medium used for HST and ink float is typically a 1% formic acid solution dyed green, while the other tests typically use water, except for edge wicking, which can use a different medium than those described herein.

[0100] As used herein, the terms “fixation,” “fixing,” and “fix” mean that a substance is at least temporarily or permanently bound to or attached to a fiber.

[0101] As used herein, the terms “polymer” or “polymer additive” and similar terms are used in the ordinary sense understood by those skilled in the art and are therefore used herein to refer to or describe macromolecules (or groups of such molecules) that may contain repeating units. Polymers can be formed in a variety of ways, including by polymerizing monomers and / or by chemically modifying one or more repeating units of a precursor polymer. Unless otherwise specified, polymers may contain “homopolymers” that may contain substantially the same repeating units, which can be formed, for example, by polymerizing a particular monomer. Unless otherwise specified, polymers may also contain “copolymers” that may contain two or more different repeating units, which can be formed, for example, by copolymerizing two or more different monomers and / or by chemically modifying one or more repeating units of a precursor polymer. Unless otherwise stated, polymers or copolymers may also contain “terpolymers” or “quaternary copolymers,” which generally refer to polymers containing three, four, or more different repeating monomer units. Any of the one or more polymers discussed herein can be used in any applicable process, such as as a primary emulsifier in the formation of ASA sizing emulsions.

[0102] As used herein, the term "monomer" generally refers to nonionic monomers, anionic monomers, cationic monomers, zwitterionic monomers, betaine monomers, and zwitterionic-pair monomers.

[0103] As used herein, the term "anionic monomer" can refer to an anionic monomer that is substantially all or part (in equilibrium) anionic in a pH range of about 4.0 to about 9.0. An "anionic monomer" can be neutral at low pH (pH from about 2 to about 6) or anionic at low pH.

[0104] As used herein, the term "cationic monomer" generally refers to a monomer that has a positive charge or a monomer that is positively charged at pH within the normal operating range of the papermaking process.

[0105] As used herein, the term "water-soluble" generally refers to a polymer article that is completely miscible with water. When mixed with an excess of water, the cationic emulsion polymer in the polymer article preferably dissolves completely, and the resulting polymer solution preferably does not contain discrete polymer particles or particles.

[0106] As used herein, the terms "aqueous solution" or "solution" generally refer to a mixture of water and one or more completely dissolved water-soluble solutes. The solution may be homogeneous. When mixed with excess water, the cationic emulsion polymer in the polymer article preferably dissolves completely, and the resulting polymer solution preferably does not contain discrete polymer particles or fragments.

[0107] As used in this article, the term "wet end of the paper machine" or "wet end" generally refers to the portion of the papermaking process between pulping (or bleaching) and wet pressing.

[0108] The terms “total solids” or “total suspended solids” are used interchangeably herein and generally refer to the total amount or weight of suspended solids (such as one type of cellulose fiber, multiple types of cellulose fibers, and mineral pigments) contained in an aqueous medium. “Total solids” or “total suspended solids” generally does not include dissolved solids.

[0109] As used herein, the term “lbs / ton” or “# / T” indicates the dry mass pounds of material (e.g., ASA weight per gross dry tonne of suspended solids) added per tonne of suspended solids.

[0110] As used herein, the phrase “wt.%” means the dry weight of additives in a formulation, solution, or slurry multiplied by 100% of the dry weight of solids.

[0111] The term "alkenyl succinic anhydride" or "ASA" generally refers to an alkenyl succinic anhydride compound consisting of a monounsaturated hydrocarbon chain containing a side-chain succinic anhydride group. Alkenyl succinic anhydride compounds are typically liquids and can be derived from maleic anhydride and suitable alkenes. Alkenyl succinic anhydride compounds can also be solids.

[0112] ASA sizing agents that can be used in the subject matter of this invention are generally described by the following structural formula:

[0113]

[0114] Where R represents a dimethylene or trimethylene group, and R is a hydrophobic group containing 5 or more carbon atoms, which can be selected from the group consisting of: alkyl group, alkenyl group, aralkyl group or areneyl group.

[0115] Generally, alkenyl succinic anhydride compounds can be prepared by reacting isomerized C14-C20 monoolefins (preferably in excess of the inner olefin) with maleic anhydride at a temperature and time sufficient to form the alkenyl succinic anhydride compound.

[0116] If the olefin used to prepare the alkenyl succinic anhydride compound is not an internal olefin (e.g., in the case of an α-olefin), it may be preferable to first isomerize the olefin to provide an internal olefin. The olefin that can be used to prepare the alkenyl succinic anhydride compound can be straight-chain or branched. Preferably, the olefin can contain at least about 14 carbon atoms. Typical structures of alkenyl succinic anhydride compounds are disclosed, for example, in U.S. Patent No. 4,040,900, which is incorporated herein by reference in its entirety. Alkenyl succinic anhydride compounds and methods for their preparation are described, for example, in C.E. Farley and R.B. Wasser, “The Sizing of Paper, Second Edition”, edited by W.F. Reynolds, Tappi Press, 1989, pp. 51-62, the disclosure of which is hereby incorporated herein by reference in its entirety.

[0117] The alkenyl succinic anhydride component may contain some hydrolyzed alkenyl succinic anhydride. Based on the total weight of the alkenyl succinic anhydride component, the amount of hydrolyzed alkenyl succinic anhydride can range from about 1 wt.% to about 99 wt.%. Based on the total weight of the emulsion, the alkenyl succinic anhydride component is typically present in the emulsion in an amount of at least about 0.01 wt.%, or about 0.1 wt.% to about 20 wt.%, or about 0.3 wt.% to about 15 wt.%. In another embodiment, the alkenyl succinic anhydride component is present in the emulsion in an amount of about 20 wt.% to about 40 wt.%.

[0118] As used herein, the terms “starch” and “cationic starch” generally refer to cationic agents, various cationic starch derivatives, including primary, secondary, tertiary, or quaternary ammonium starch derivatives and other cationic nitrogen-substituted starch derivatives, as well as cationic sulfonium and phosphonium starch derivatives. The patent holder states that such derivatives can be made from all types of starch, including corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, rice starch, barley starch, pea starch, sweet potato starch, and any combination thereof.

[0119] Cationic starch can be formulated prior to its use in papermaking processes by methods such as dissolving dry cationic starch in water; cooking by methods including, but not limited to, spray cooking, steam cooking, or pot cooking; and cooling to a temperature ranging from 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, to obtain a cooked starch solution with a solids percentage ranging from 1-10%, 2-8%, or 3-6% by mass; or obtaining a pregelatinized cationic starch with a solids percentage ranging from 20% to 40% by mass, and diluting it with water to obtain a pregelatinized starch solution with a solids percentage ranging from 1-10%, 2-8%, or 3-6% by mass. Any of the one or more starches discussed herein can be used in any suitable process, for example, as a secondary emulsifier in the formation of ASA sizing emulsions.

[0120] Methods used to measure the molecular weight of polymers include light scattering, osmotic pressure, and viscosity. These methods allow for the acquisition of average molecular weight values. However, many polymers are not composed of molecules of a single molecular weight, but rather of a collection of molecules with many different molecular weights.

[0121] As used herein, the terms "molecular weight" or "weight-average molecular weight" or "MW" refer to the weight fraction of molecules in a polymer sample. The MW of a polymer can be determined by gel permeation chromatography (GPC), a size exclusion chromatography (SEC) method. This chromatographic method is primarily used to measure the molecular weight of polymer compounds based on retention times on size exclusion columns under standardized conditions. Other methods for determining the weight-average molecular weight of polymers include light scattering and ultracentrifugation.

[0122] As used herein, the phrase "stirring with sufficient energy" or "emulsification by stirring with sufficient energy" generally refers to high-shear stirring of ASA to provide an emulsion and achieve sufficient mixing. The mixing apparatus used to mix the components of the ASA emulsion must produce an emulsion with sufficient stability (e.g., 1-2 hours, 1-20 hours, 1-24 hours, or 1-48 hours), sufficient average particle size (e.g., diameter not exceeding 3, 2, or 1 μm), sufficient particle size distribution (e.g., 95% of the particles having a diameter not exceeding 3 μm), and sufficient intrinsic viscosity (e.g., not exceeding 100 cP, when measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20°C) for use as a sizing emulsion at the wet end of a paper machine. Before adding the ASA emulsion of the present invention to the paper machine, the components of the emulsion are typically exposed to a mixing pump to achieve mixing of the relevant components of these emulsions. Mixing can be achieved in several ways (e.g., static mixing, pump mixing, online mixing, or any mixing method known in the art). The components of the ASA sizing emulsion of the present invention can be added to the feed side of a pump capable of forming an emulsion. The discharge from this pump can be separated, with a portion of the discharge entering the paper machine and another portion returning to the pump's feed point. By controlling the percentage of the pump output that is recycled back to the pump's feed point, the amount of energy exposed to the emulsion components can be controlled, thereby controlling the quality of the emulsion formed from the ASA sizing emulsion components. Sufficient energy usage, controlled by the output regeneration rate, can control the particle size of the ASA sizing agent emulsion within the aforementioned range. By controlling the output-to-feedback ratio of the emulsifying pump, the particle size of the emulsion can be controlled to achieve the desired physical properties of these ASA emulsion sizing agents. Alternatively, the emulsion forming pump can be operated such that no discharge is regenerated to the feed point. To obtain sufficient emulsion quality, it is preferable to operate the pump at pressures exceeding atmospheric pressure.

[0123] Detailed description of the invention

[0124] This invention generally relates to compositions and methods for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard. In particular, this disclosure provides a method for co-emulsifying ASA using a cationic polymer as a primary emulsifier and cationic starch as a secondary emulsifier, which imparts excellent stability to the emulsion and enhances sizing performance in high-ash papermaking with a significantly reduced total starch utilization rate compared to conventional natural polymer ASA emulsification applications.

[0125] Sizing is a process that reduces the amount of fluid absorbed by dry paper or paperboard. Sizing improves water resistance, reduces fluid penetration, and prevents ink and print from becoming blurred. Two common methods are internal sizing and surface sizing. Internal sizing is widely used for a wide variety of papers, while surface sizing is typically used to produce higher-grade papers.

[0126] Internal sizing involves treating the fiber pulp with a sizing agent, making the paper resistant to fluid absorption. Internal sizing agents are added to the fibers at the wet end of the papermaking process and typically form a strong bond with the fibers. Desired properties of internal sizing agents include high hydrophobicity, high retention on the fibers, and uniform distribution throughout the fibers. Alkyl succinic anhydride (ASA) is a commonly used internal sizing agent, which reacts with the hydroxyl groups on cellulose fibers via esterification, thereby anchoring it to the fibers. The alkyl or alkenyl side chains of ASA impart hydrophobicity to the cellulose material. Highly effective internal sizing agents reduce the amount of fluid absorbed by the paper as measured by, but not limited to, the Cobb test, Hercules sizing test, edge wicking, water droplets, ink float, or any combination thereof.

[0127] ASA sizing agents are often hydrophobic and typically must be used in aqueous papermaking systems. Obtaining a uniform, stable ASA emulsion suitable for papermaking requires considerable effort. Formulating the aforementioned types of ASA sizing agents presents significant problems for applying the sizing agent before the paper raw material or pulp is formed into sheets or other useful forms. Part of the problem is that ASA sizing materials are insoluble in water and therefore must be uniformly suspended in the pulp so that the sizing agent can fully contact the cellulose fibers to achieve the desired effect in the final product.

[0128] Additives will act as emulsifiers or dispersers of ASA sizing agents in the pulp and allow the sizing agents to remain on the fibers. Cationic agents (e.g., various starch derivatives) have been successfully used as emulsifiers along with other emulsifiers to form ASA emulsions suitable for papermaking with stable, viscous, and particle size properties.

[0129] Currently, the availability of starch for commercial applications is severely limited due to supply chain shortages. This invention utilizes a dual-emulsification technology, employing a cationic solution polymer in the primary emulsification step, followed by secondary emulsification of the starch at a low dose under shear. Compared to conventional natural polymer ASA emulsification applications, dual emulsification imparts superior emulsion stability with a significantly reduced total starch utilization rate and improves sizing performance in high-ash papermaking.

[0130] On one hand, the present invention provides a method for preparing a stable alkenyl succinic anhydride (ASA) sizing emulsion suitable for manufacturing paper and paperboard, the method comprising:

[0131] (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent;

[0132] (b) Combining and emulsifying the ASA sizing agent with a primary emulsifier to form a primary emulsion; and

[0133] (c) Following step (b), a secondary emulsifier is added and emulsified to form the ASA sizing emulsion, and

[0134] (d) Optionally, after steps (a) to (c), the resulting stable ASA sizing emulsion is added to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp.

[0135] In some exemplary embodiments, the method further includes, after step (c):

[0136] (a) Adding the ASA sizing emulsion to the papermaking pulp, pulp, or fiber raw material; or

[0137] (b) The ASA sizing emulsion is added to the high-ash content pulp, the high-ash content pulp comprising ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof, wherein the high-ash content pulp comprises 1-35%, 2-30%, 5-25%, or 10-20% ash content by weight, preferably 5-25% ash by weight. Typically, the ideal ash content range for wood-free communication paper and specialty paper is 5%-25%.

[0138] In some exemplary embodiments, the ASA sizing agent comprises:

[0139] (a) ASA solid, ASA waxy solid, ASA waxy liquid, ASA liquid, or mixtures thereof; and

[0140] (b) A single ASA sizing agent or a mixture of ASA sizing agent molecules and / or isomers.

[0141] In some exemplary embodiments of the method, (i) the primary emulsifier comprises an aqueous polymer solution containing one or more cationic polymers and water; and (ii) the secondary emulsifier comprises one or more cationic starches.

[0142] In some exemplary embodiments, the polymer aqueous solution comprises one or more cationic polymers in the range of 1-70%, 2-50%, or 5-30% by solid weight.

[0143] In some exemplary embodiments, the one or more cationic polymers comprise:

[0144] (a) One or more synthetic copolymers, terpolymers, or quaternaries comprising acrylamide and one or more cationic monomers, wherein the one or more cationic monomers are selected from the group consisting of:

[0145] (i) diallyl dialkyl ammonium halides, including but not limited to diallyl dimethyl ammonium chloride (“DADMAC”) and diallyl diethyl ammonium chloride;

[0146] (ii) N,N-dialkylaminoalkyl acrylates, (meth)acrylates, and their acid addition salts and / or quaternary ammonium salts, including but not limited to acryloyloxyethyltrimethylammonium chloride (“AETAC”), methacryloyloxyethyltrimethylammonium chloride (“MAETAC”), dimethylaminoethyl acrylate (“DMAEA”) and its acid addition salts, dimethylaminoethyl methacrylate (“DMAEMA”) and its acid addition salts, dimethylaminoethyl acrylate methyl sulfate quaternary ammonium salt, dimethylaminoethyl acrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl acrylate sulfate, dimethylaminoethyl acrylate hydrochloride, diethylaminoethyl acrylate, methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate sulfate, dimethylaminoethyl methacrylate hydrochloride, dimethylaminoethyl methacryloyl hydrochloride;

[0147] (iii) N,N-dialkylaminoalkylacrylamides and N,N-dialkylaminoalkyl(methyl)acrylamides and their acid addition salts or quaternary ammonium salts, including but not limited to acrylamidopropyltrimethylammonium chloride (“APTAC”), methacrylamidopropyltrimethylammonium chloride (“MAPTAC”), dimethylaminopropylacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylacrylamide sulfate, dimethylaminopropylacrylamide hydrochloride, dimethylaminopropylmethacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylmethacrylamide sulfate, dimethylaminopropylmethacrylamide hydrochloride, diethylaminoethyl acrylate, diethylaminoethyl methacrylate; or

[0148] Any combination of (iv)(i)-(iii);

[0149] (b)(a) one or more synthetic copolymers, terpolymers or quaternaries, wherein the one or more synthetic copolymers, terpolymers or quaternaries optionally contain

[0150] (i) one or more other nonionic monomers selected from the group consisting of: methacrylamide; N-alkylacrylamide, including but not limited to N-methacrylamide, N-ethylacrylamide, N-propylacrylamide and N-butylacrylamide; N,N-dialkylacrylamide, including but not limited to N,N-dimethylacrylamide and N,N-diethylacrylamide; N-alkylmethylacrylamide; alkyl acrylate; hydroxyalkyl acrylate and hydroxyalkyl methacrylate, including but not limited to methyl acrylate, 2-hydroxyethyl acrylate and 3-hydroxypropyl acrylate. 4-Hydroxybutyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate; dialkyl acrylates and dialkyl methacrylates, including but not limited to 2,3-dihydroxypropyl acrylate, 3,4-dihydroxybutyl acrylate, 2,3-dihydroxypropyl methacrylate (DHPMA), and 3,4-dihydroxybutyl methacrylate; alkyl acrylates, including but not limited to methyl methacrylate; acrylonitrile; N-vinylmethylacetamide, N-vinylmethylformamide; N-vinyl acetate, glyoxalated acrylamide, and vinylpyrrolidone;

[0151] (ii) One or more additional anionic monomers selected from the group consisting of: acrylic acid, methacrylic acid, sulfonic acid, phosphonic acid, and their alkali metal salts, alkaline earth metal salts, and ammonium salts, including but not limited to acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamidomethanesulfonic acid, acrylamidoethanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid; or

[0152] Any combination of (iii)(i)-(ii);

[0153] (c) One or more cationic glyoxalized polyacrylamide (GPAM) polymers, said one or more cationic GPAM polymers being obtained by reacting glyoxal with one or more synthetic copolymers, terpolymers or quaternary copolymers of (a), one or more synthetic copolymers, terpolymers or quaternary copolymers of (b), or combinations thereof;

[0154] (d) One or more semi-synthetic polymers comprising (a) or (b) the one or more synthetic copolymers, terpolymers, or quaternary copolymers optionally grafted onto one or more natural polymers, including but not limited to starch, chitin, chitosan, and natural polysaccharides; or

[0155] (e)(a) to (d) any combination

[0156] And the one or more cationic polymers said therein have a weight-average molecular weight in the range of 10,000-3,000,000 Da, 10,000-2,000,000 Da, 10,000-1,000,000 Da, 10,000-500,000 Da, 10,000-200,000 Da, 10,000-100,000 Da or 10,000-50,000 Da.

[0157] In some exemplary embodiments, the one or more cationic starches:

[0158] (a) A cationic modified or unmodified starch comprising one or more of the following groups: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, rice starch, barley starch, pea starch, sweet potato starch, and any combination thereof; and

[0159] (b) having a nitrogen content percentage (N%) ranging from 0.2-2%, 0.2-1.75%, 0.2-1.5%, 0.2-1.25%, 0.2-1% or 0.25-0.45% by mass, preferably 0.35-1.45% by mass.

[0160] In some exemplary embodiments, the one or more cationic starches are formulated by a method comprising the following steps before being added to the ASA sizing agent:

[0161] (a) Dissolving dry cationic starch in water; cooking by methods including but not limited to spray cooking, steam cooking, or pot cooking; and cooling to a temperature in the range of 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, to obtain a cooked starch solution with a solid percentage in the range of 1-10%, 2-8%, or 3-6% by mass; or

[0162] (b) Obtain a pregelatinized cationic starch with a solid percentage ranging from 20% to 40% by mass, and dilute it with water to obtain a pregelatinized starch solution with a solid percentage ranging from 1-10%, 2-8%, or 3-6% by mass.

[0163] In some exemplary embodiments of the method, (i) the one or more cationic polymers are selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) quaternary copolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer, and (ii) the one or more cationic starches comprise corn starch, waxy corn starch, potato starch, cassava starch, wheat starch, or pea starch.

[0164] In some exemplary embodiments, the method includes one or more of the following:

[0165] (a) Adding the primary emulsifier to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and

[0166] (b) The secondary emulsifier is added to the primary emulsion to obtain a dry starch to ASA mass ratio of 0.25:1 to 2:1, 0.3:1 to 1.6:1, 0.4:1 to 1.2:1 or 0.5:1 to 1:1.

[0167] In some exemplary embodiments, the method includes:

[0168] (a) The primary emulsifier is added to the ASA sizing agent at ambient temperature and emulsified by stirring with an energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm; and / or

[0169] (b) The secondary emulsifier is added to the primary emulsion at a temperature in the range of 20-80°C, 20-60°C, 20-40°C or 20-25°C, preferably 20-40°C, and emulsification is carried out by stirring with energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm or 0.5-1 μm.

[0170] In some exemplary embodiments, the ASA sizing emulsion in its final form is as follows:

[0171] (a) Includes median particle sizes with diameters ranging from 0.5–1 μm, 0.6–0.9 μm, or 0.7–0.8 μm;

[0172] (b) Viscosities ranging from 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP, or 50-60 cP when measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C.

[0173] (c) It exhibits stability over 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours, or 1-48 hours, wherein the stability is determined by the ASA sizing emulsion, and the ASA sizing emulsion retains...

[0174] (i) The median particle size has a diameter of 0.5-3 μm, 0.5-2 μm, 0.5-1 μm, 0.6-0.9 μm or 0.7-0.8 μm, preferably less than 1 μm;

[0175] (ii) When measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C, the viscosity ranges from 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP or 50-60 cP, preferably less than 100 cP.

[0176] (d) Add immediately to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp, or store in a tank or holding facility for 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours or 1-48 hours before adding the ASA sizing emulsion to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp;

[0177] (e) Compared to ASA sizing emulsions prepared by a single or dual emulsification method using one or more emulsifiers containing one or more cationic starches, it contains a reduced final mass ratio of dry starch to ASA; or

[0178] Any combination of (f)(a)-(e).

[0179] In some exemplary embodiments, when the stabilized alkenyl succinic anhydride (ASA) sizing emulsion is used as a sizing agent during the manufacture of the paper or paperboard, it produces sheet products selected from the group consisting of: high ash paper or paperboard, printing or writing grade paper or paperboard, alkaline printing or writing grade paper or paperboard, bleached paper or paperboard, packaging grade paper or paperboard, and partially recycled or 100% recycled paper or paperboard, wherein the sheet products contain optimal sizing performance as determined by industry-standardized testing, including but not limited to HST, Cobb, water droplet test, contact angle, edge wicking, or water permeability, wherein the optimal sizing performance is determined relative to an equivalent sheet product comprising an ASA sizing emulsion prepared by a monoemulsification or doubulsification method using one or more emulsifiers containing one or more cationic starches.

[0180] On the other hand, the present invention provides a dual emulsification method for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard, the method comprising:

[0181] (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent;

[0182] (b) The ASA sizing agent is combined with a primary emulsifier and emulsified at ambient temperature, and stirred with energy sufficient to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming a primary emulsion; and

[0183] (c) Following step (b), a secondary emulsifier is added and emulsified at a temperature ranging from 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, and stirred with sufficient energy to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming the ASA sizing emulsion, and

[0184] (d) Optionally, after step (c), the ASA sizing emulsion is added to the high-ash paper pulp.

[0185] in

[0186] (i) The primary emulsifier comprises an aqueous polymer solution containing an acrylamide cationic copolymer selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) tetropolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer;

[0187] (ii) The secondary emulsifier comprises one or more cationic modified or unmodified starches selected from the group consisting of: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, pea starch, and mixtures thereof;

[0188] (iii) The high-ash paper pulp comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof;

[0189] (iv) The high-ash pulp contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5%-25% ash by weight;

[0190] (v) The primary emulsifier is added to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and

[0191] (vi) The secondary emulsifier is added to the primary emulsion to obtain a dry starch to ASA mass ratio of 0.25:1 to 2:1, 0.3:1 to 1.6:1, 0.4:1 to 1.2:1 or 0.5:1 to 1:1.

[0192] On the other hand, the present invention provides an ASA sizing emulsion composition or a papermaking pulp, pulp or fiber raw material comprising the ASA sizing emulsion composition, optionally a high ash pulp, wherein the ASA sizing emulsion composition or papermaking pulp, pulp or fiber raw material can be obtained by the method according to any one of the foregoing.

[0193] On the other hand, the present invention provides a method for producing paper or paperboard, the method comprising obtaining a high ash distribution pulp comprising wood pulp, optionally comprising a fiber raw material comprising a high content of recycled fiber and / or factory waste paper fiber, optionally a coarse fiber raw material, optionally a bleached fiber raw material, optionally containing process water from pulp, paper or paperboard production; and treating the fiber raw material at the wet end of a paper machine with an ASA sizing emulsion according to any one of the preceding claims, wherein:

[0194] (a) The high-ash slurry comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof; and

[0195] (b) The high ash content slurry contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5-25% ash by weight.

[0196] The methods and compositions illustratively disclosed herein may be practiced in the absence of any elements not specifically disclosed herein and / or any elements specifically disclosed herein. Exemplary embodiments of the invention and their advantages will be further disclosed in the following examples.

[0197] Example

[0198] The embodiments provided herein are for illustrative purposes only, in order to provide a more complete understanding of the invention. These embodiments should not be construed as limiting the invention in any way.

[0199] Example 1: A dual-emulsification method for preparing alkenyl succinic anhydride (ASA) sizing emulsions

[0200] ASA sizing emulsions were prepared to evaluate their sizing effect on paper or paperboard. The biemulsification method of this invention, which uses a cationic solution polymer as a primary emulsifier in the primary emulsification step and then performs secondary emulsification under shear using a low dose of cationic starch as a secondary emulsifier, was compared with conventional emulsification techniques that use starch only as a control. Figure 1 An exemplary flowchart is shown for conventional emulsification of ASA and the dual emulsification method (novel two-step method) of the present invention.

[0201] Dual emulsification method

[0202] Alkenyl succinic anhydride (ASA) sizing emulsions were prepared in the laboratory via a double emulsification process, while ensuring that the shear rate and time of all emulsions remained constant.

[0203] A primary emulsifier was prepared from an aqueous solution of a cationic polymer of acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer (polymer 1).

[0204] A secondary emulsifier is prepared by cooking dry cationic modified corn starch in a jet cooker to obtain a liquid starch solution (cooked starch, i.e., factory-cooked wet-end cationic starch) with a working solids content of 3-6% by mass. The nitrogen content of the starch is 0.25-0.45% by mass. Alternatively, pregelatinized starch can be obtained, with a typical solids content in the range of 20-40% by mass. This pregelatinized solution can be diluted on-site with water to the desired working solids range of 3-6% by mass.

[0205] according to Figure 2 A primary emulsifier containing an acrylamide-based polymer solution is added to an alkenyl succinic anhydride (ASA) sizing agent at a mass ratio of 0.8:1 or 1:1. Primary emulsification is performed at room temperature (20°C) using a high-shear pump until complete emulsification forms a primary emulsion.

[0206] After a short period of time (less than 10 minutes), a secondary emulsifier is added to the primary emulsion mixture, with the secondary emulsifier (starch) to ASA mass ratio of 0.5:1 to 2:1, and according to... Figure 2 Secondary emulsification is performed using a high-shear pump at room temperature (20°C) or high temperature (80°C) until complete emulsification is achieved to form a double-emulsified (secondary) ASA sizing emulsion.

[0207] Conventional (control) emulsification method

[0208] According to standard techniques, control emulsions for monoemulsification and biemulsification were prepared using the same cooked starch emulsifier described in the biemulsification method.

[0209] according to Figure 2 For the control sample with single emulsification, in the primary emulsification step, the cooked starch emulsifier was added to the alkenyl succinic anhydride (ASA) sizing agent at room temperature (20°C) in a mass ratio of 4:1 (starch to ASA). Emulsification was performed using a high-shear pump until complete emulsification.

[0210] according to Figure 2 For the control sample with single emulsification, in the primary emulsification step, the cooked starch emulsifier was added to the alkenyl succinic anhydride (ASA) sizing agent at room temperature (20°C) in a mass ratio of 2:1 or 4:1 (starch to ASA). Figure 2For the control sample undergoing dual emulsification, secondary emulsification was performed by adding the same cooked starch emulsifier at a 2:1 mass ratio (starch to ASA) at room temperature (20°C). Primary and secondary emulsification were carried out using a high-shear pump until complete emulsification.

[0211] Thorough emulsification is determined by the presence of a median ASA particle size range of 0.5–3 μm, 0.5–2 μm, or 0.5–1 μm in the emulsion, and an ASA particle size distribution in which 95% of the ASA particles have a diameter not exceeding 3 μm.

[0212] Evaluation of ASA emulsion

[0213] The particle size and viscosity of primary, secondary, and control ASA emulsions prepared by the biemulsification method according to the present invention and by a conventional (control) emulsification method were analyzed.

[0214] The median particle size (median PS) and maximum particle size (95% diameter) of the primary, secondary, and control ASA emulsions were analyzed immediately after emulsification. The initial viscosity of the secondary and control ASA emulsions was also analyzed immediately after emulsification. To determine the relative stability of the emulsions, the secondary and control ASA emulsions were aged at room temperature (20°C) for 2 hours, and then the final particle size and final viscosity were analyzed. The particle size and viscosity results are shown in... Figure 2 middle.

[0215] For secondary emulsions before and after aging, a median particle size of less than 1 micrometer and 95% diameter of less than 3 μm are considered desirable for laboratory papermaking applications. Due to the shear mechanics of the emulsification equipment, which enables emulsions with lower particle sizes, the optimal particle size distribution for field applications is lower.

[0216] The results showed that the dual-emulsified ASA samples prepared using a cationic polymer as the primary emulsifier (polymer 1) and starch as the secondary starch emulsifier exhibited good particle size. The median secondary particle size of all dual-emulsified ASA samples was below 1 μm before and after 2 hours of maintenance. The final 95% diameter value was also well below 3 μm for all dual-emulsified ASA samples. These particle size results demonstrate that the dual-emulsification method of the present invention provides a highly desirable particle size distribution, stable for at least 2 hours.

[0217] The optimal final particle size results were achieved using a polymer 1 to ASA ratio of 0.8:1 in the primary emulsifier and a starch to ASA ratio of 0.5:1 in the secondary emulsifier. Surprisingly, these particle size results were comparable to or better than control samples prepared using only starch at a higher starch to ASA ratio (e.g., a total of 4:1).

[0218] When measured at 60 rpm and 20°C using a Brookfield viscometer with a No. 62 rotor, the viscosity at 100 cP after a 2-hour holding time indicates good emulsion stability and is considered desirable for papermaking applications.

[0219] The viscosity results of the dual-emulsified ASA samples of this invention fully demonstrate the good ASA emulsion stability. All dual-emulsified ASA samples exhibited initial viscosity results below 100 cP, and more than two-thirds of the samples maintained a viscosity below 100 cP after holding for 2 hours, indicating good emulsion stability. Surprisingly, these are comparable to or better than control samples prepared using only starch at a higher starch-to-ASA ratio (e.g., a total of 4:1). In contrast, all control samples exhibited extremely poor final viscosity results, indicating poor stability.

[0220] Surprisingly, the dual emulsification method of the present invention can reduce the total starch requirement by 75-80% while achieving the same or enhanced particle size and stability based on viscosity.

[0221] Without being bound by theory, the mechanical principle behind these surprising results is that the primary emulsification step using a polymer as the primary emulsifier produces smaller and narrower particle sizes compared to those formed using cooked starch as the primary emulsifier. The smaller surface area means less starch is needed in the secondary steps to obtain an emulsion with comparable or superior stability. Furthermore, the use of a shear pump during the secondary emulsification step facilitates starch incorporation into the particles, further reducing starch usage. Typically, in conventional methods, shear pumping is only performed during the initial emulsification step.

[0222] Typically, ASA hydrolysis is an unwanted side reaction during emulsification, following first-order rate kinetics. Increased temperature accelerates this hydrolysis rate. Therefore, starch is usually cooled to ambient temperature before being added to ASA to slow down hydrolysis. Surprisingly, for the dual emulsification technology of this invention, starch temperatures of both 25°C and 80°C improved particle size and stability.

[0223] These results provide proof of concept that the biemulsification method of the present invention can be used to prepare biemulsified ASA sizing emulsions with enhanced emulsification properties, while using less starch compared to conventional natural polymer ASA emulsification methods.

[0224] Example 2: Evaluation of dual-emulsion ASA sizing emulsions for sizing hand papermaking

[0225] Preparation of ASA sized handmade paper

[0226] According to Example 1, a biemulsion ASA sizing emulsion and a control emulsion (containing only starch) were prepared using a cationic polymer (polymer 1) as the primary emulsifier and starch as the secondary emulsifier, under the emulsification conditions shown in Table 1. The emulsion quality of the obtained ASA emulsions was evaluated based on particle size and viscosity, and then the emulsions were used for sizing handmade paper. The results for particle size and viscosity are shown in Table 1.

[0227] Table 1: ASA emulsification conditions, particle size and viscosity measurements used in handmade paper research.

[0228]

[0229] Handmade paper was prepared on the Noble and Wood papermaking mold. The pulp was supplied by the paper mill using a high-filler (15%) HOPCC containing a blend of hardwood and softwood. ASA sizing emulsion was incorporated into the pulp. Efforts were made to simulate the mill's retention system to ensure adequate ASA retention in the handmade paper. Handmade paper was produced, and paper samples were then conditioned at 23°C and 50% relative humidity for at least one day. This followed the method outlined in "TAPPIT 402000-93: Standard Conditioning and Testing Environments for Paper, Paperboard, Pulp, Handmade Paper and Related Products".

[0230] Evaluation of handwritten paper

[0231] A Cobb test was performed to determine the mass of water absorbed by the surface of sized handmade paper over a given time period, expressed in g / m³. 2 The unit is (gsm). The lower the mass of water absorbed, the better the water resistance. For the handmade paper study, the Cobb test was performed using deionized water at 23°C for 2 minutes. The handmade paper preparation conditions (ASA dosage in lbs / ton, the ratio of primary and secondary reagents to ASA, and temperature) and Cobb results are shown in [Table / Table / Reference]. Figure 3 middle.

[0232] The Hercules sizing test (HST) was performed to measure the time required for ink penetration into handmade paper. A longer time indicates better ink resistance. For this handmade paper study, HST testing was conducted using ink with 80% reflectance and 1% formic acid. The handmade paper preparation conditions (ASA dosage in lbs / ton, ratio of primary and secondary reagents to ASA, and temperature) and HST results are shown in [Table / Insert Table ... Figure 4 middle.

[0233] The Cobb results indicate that the biemulsified ASA samples of this invention, prepared with a cationic polymer as the primary emulsifier (polymer 1) and starch as the secondary starch emulsifier, exhibit excellent sizing performance compared to the starch-only control and the polymer-1-only control. The close Cobb value groupings suggest that the sizing is uniformly dispersed throughout the sheet, rather than unevenly distributed between the top and bottom sides of the sheet.

[0234] For handmade paper made with 5# / ton ASA, almost no change in Cobb value was observed. However, a large change was observed at a dosage of 3# / ton ASA, where the dual-emulsified ASA of the present invention provided the optimal Cobb value (1° polymer:ASA ratio of 0.8:1 and 2° starch:ASA ratio of 1:1). This sample provided the lowest Cobb value with the most closely grouped data, indicating better water resistance and better sizing coverage at lower ASA dosages (3# / ton) compared to the starch and polymer controls.

[0235] For handmade paper made with 5# / ton ASA, almost no change in HST value was observed. However, a large change was observed at an ASA dosage of 3# / ton, where the dual-emulsified ASA of the present invention provided the optimal HST value (1° polymer:ASA ratio of 0.8:1 and 2° starch:ASA ratio of 1:1). This sample provided the highest HST value with the most closely grouped data, indicating better ink resistance and better sizing coverage at lower ASA dosages (3# / ton) compared to the starch and polymer controls.

[0236] These results provide proof of concept that the dual-emulsification method of the present invention can be used to prepare dual-emulsified ASA sizing emulsions with enhanced sizing properties for paper products, while using less starch compared to conventional natural polymer ASA emulsification methods. These results also provide proof of concept that the dual-emulsified ASA samples of the present invention can be effectively used as sizing agents to enhance the water and ink resistance of handmade paper.

[0237] Example 3: Evaluation of dual-emulsion ASA sizing emulsions used for sizing high-ash content slurries

[0238] The control ASA sizing emulsions were prepared according to Example 1 using only starch and only polymer. These ASA sizing emulsions were used to produce handmade paper from high ash content pulp (20% ash), and the water resistance (Cobb test) and ink resistance (HST) of the handmade paper were evaluated according to Example 2. Figure 5 The HST results are shown compared to those of starch-emulsified ASA and synthetic polymer-emulsified ASA. Figure 6 The Cobb results of the present invention, comparing the dual-emulsified ASA with starch-emulsified ASA, are shown.

[0239] Ash content typically refers to calcium carbonate, TiO2, kaolin, silicates, and other carbonate-based and kaolin-based pigments. High-ash pulps are commonly used to produce alkaline printing and writing paper.

[0240] The effectiveness of using high doses of modified natural polymers (cationic starch) as emulsifiers for ASA sizing applications in pulps containing significant ash content (up to 35%) has been well-proven. In the presence of ash, sizing typically adheres rapidly to the ash surface, and the sizing agent is lost if the ash-sizing mixture is not retained in the paper. Therefore, it is crucial for alkaline printing and writing-grade paper and paperboard (including packaging materials) to have ASA sizing emulsions that are effectively retained in the paper and do not lose with the ash.

[0241] Figure 5 This study demonstrates the effectiveness of starch-emulsified ASA compared to synthetic polymer-emulsified ASA in high-quality paper pulp containing 20% ​​ash. When using synthetic polymers as emulsifiers in ASA sizing emulsions for sizing high-ash paper pulp, their limitation of only providing water resistance is evident.

[0242] Figure 6 An exemplary bar graph of Cobb values ​​is shown, indicating that ASA emulsions prepared using the dual emulsification method of the present invention (red bars) have similar sizing properties compared to starch alone (blue bars). Figure 6 The invention demonstrates a dual emulsification method for ASA sizing, which uses a synthetic polymer in the primary emulsification and then applies a low dose of cationic starch in the secondary emulsification, significantly reducing starch usage without compromising sizing effect.

[0243] These results further provide proof of concept that the biemulsification method of the present invention can be used as a sizing agent to achieve sizing performance comparable to or better than that of high-dose starch, while significantly reducing the total amount of starch used.

[0244] Example 4: Extended stability of dual-emulsified ASA sizing emulsion

[0245] A dual-emulsified ASA sizing emulsion was prepared according to Example 1 and maintained for 48 hours. Observation and analysis were performed by particle size determination and viscosity measurement. Prior to analysis, the sample was stored in a glass jar at room temperature (20°C). Stability can be assessed based on the median particle size or particle size distribution of the emulsion. Specifically, for median particle size, the emulsion is considered stable when the median particle size remains below a specified value for a given period after emulsification. For particle size distribution, the emulsion is considered stable when at least 95% of the particles are smaller than a specified value for a given period after emulsification. The median particle size or the specified particle size can be [e.g., a range between 0.5 μm and 3 μm]. The given period can be [e.g., a range between 1 minute and 48 hours]. For example, in a laboratory setting, the emulsion is considered stable when, after a laboratory emulsification process, the median particle size or at least 95% of the particles are smaller than 3 μm. In industrial environments, emulsions are likely stable once the emulsification process is complete and the median particle size, or at least 95% of the particles, is less than 2 micrometers. Typically, emulsions are used in papermaking processes 1 to 10 minutes, 10 minutes to 1 hour, or 1 hour to 4 hours after emulsification.

[0246] Extended stability tests were conducted to determine the extended stability of the biemulsified ASA sizing emulsion of the present invention compared to a control ASA emulsion prepared using a conventional starch emulsifier. The particle size distribution and viscosity measurements over time, reflecting the emulsion stability, are shown in Table 2.

[0247] These extended stability results further provide proof of concept that the biemulsification method of the present invention can be used to form very stable ASA sizing emulsions that can be temporarily stored for up to 48 hours in field or off-site storage facilities or holding tanks for later use. These results are particularly advantageous for recycled paperboard applications.

[0248] Table 2: Particle size and viscosity stability of ASA emulsions prepared by the dual emulsification technology of the present invention.

[0249]

Claims

1. A method for preparing a stable alkenyl succinic anhydride (ASA) sizing emulsion suitable for manufacturing paper and paperboard, the method comprising: (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent; (b) Combining and emulsifying the ASA sizing agent with a primary emulsifier to form a primary emulsion; and (c) Following step (b), a secondary emulsifier is added and emulsified to form the ASA sizing emulsion, and (d) Optionally, after steps (a) to (c), the resulting stable ASA sizing emulsion is added to paper pulp, pulp or fiber raw material, optionally high ash pulp.

2. The method according to claim 1, wherein the method further comprises, after step (c): (a) Add the ASA sizing emulsion to the papermaking pulp, pulp or fiber raw material; or (b) Add the ASA sizing emulsion to the high ash content slurry, the high ash content slurry comprising ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof, wherein the high ash content slurry comprises 1-35%, 2-30%, 5-25%, or 10-20% ash content by weight, preferably 5%-25% ash by weight.

3. The method according to claim 1 or 2, wherein the ASA sizing agent comprises: (a) ASA solid, ASA waxy solid, ASA waxy liquid, ASA liquid, or mixtures thereof; and (b) A single ASA sizing agent or a mixture of ASA sizing agent molecules and / or isomers.

4. The method according to any one of claims 1 to 3, wherein (i) the primary emulsifier comprises an aqueous polymer solution comprising one or more cationic polymers and water; and (ii) the secondary emulsifier comprises one or more cationic starches.

5. The method according to any one of claims 1 to 4, wherein the polymer aqueous solution comprises one or more cationic polymers in the range of 1-70%, 2-50%, or 5-30% by solid weight.

6. The method according to any one of claims 1 to 5, wherein the one or more cationic polymers comprise: (a) One or more synthetic copolymers, terpolymers, or quaternaries comprising acrylamide and one or more cationic monomers, wherein the one or more cationic monomers are selected from the group consisting of: (i) diallyl dialkyl ammonium halides, including but not limited to diallyl dimethyl ammonium chloride ("DADMAC") and diallyl diethyl ammonium chloride; (ii) N,N-dialkylaminoalkyl acrylates, (meth)acrylates, and their acid addition salts and / or quaternary ammonium salts, including but not limited to acryloyloxyethyltrimethylammonium chloride ("AETAC"), methacryloyloxyethyltrimethylammonium chloride ("MAETAC"), dimethylaminoethyl acrylate ("DMAEA") and its acid addition salts, dimethylaminoethyl methacrylate ("DMAEMA") and its acid addition salts, dimethylaminoethyl acrylate methyl sulfate quaternary ammonium salt, dimethylaminoethyl acrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl acrylate sulfate, dimethylaminoethyl acrylate hydrochloride, diethylaminoethyl acrylate, methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate methyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate benzyl chloride quaternary ammonium salt, dimethylaminoethyl methacrylate sulfate, dimethylaminoethyl methacrylate hydrochloride, dimethylaminoethyl methacryloyl hydrochloride; (iii) N,N-dialkylaminoalkylacrylamides and N,N-dialkylaminoalkyl(methyl)acrylamides and their acid addition salts or quaternary ammonium salts, including but not limited to acrylamidopropyltrimethylammonium chloride ("APTAC"), methacrylamidopropyltrimethylammonium chloride ("MAPTAC"), dimethylaminopropylacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylacrylamide sulfate, dimethylaminopropylacrylamide hydrochloride, dimethylaminopropylmethacrylamide methyl sulfate quaternary ammonium salt, dimethylaminopropylmethacrylamide sulfate, dimethylaminopropylmethacrylamide hydrochloride, diethylaminoethyl acrylate, diethylaminoethyl methacrylate; or Any combination of (iv)(i)-(iii); (b)(a) one or more synthetic copolymers, terpolymers or quaternaries, wherein the one or more synthetic copolymers, terpolymers or quaternaries optionally contain (i) one or more additional nonionic monomers, said additional nonionic monomers being selected from the group consisting of: methacrylamide; N-alkylacrylamide. Including but not limited to N-methacrylamide, N-ethylacrylamide, N-propylacrylamide, and N-butylacrylamide; N,N-dialkylacrylamide, including but not limited to N,N-dimethylacrylamide and N,N-diethylacrylamide; N-alkylmethylacrylamide; alkyl acrylates; hydroxyalkyl acrylates and hydroxyalkyl methacrylates, including but not limited to methyl acrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate; dialkyl acrylates and dialkyl methacrylates, including but not limited to 2,3-dihydroxypropyl acrylate, 3,4-dihydroxybutyl acrylate, 2,3-dihydroxypropyl methacrylate (DHPMA), and 3,4-dihydroxybutyl methacrylate; alkyl acrylates, including but not limited to methyl methacrylate; acrylonitrile; N-vinylmethylacetamide, N-vinylmethylformamide; N-vinyl acetate, glyoxalated acrylamide, and vinylpyrrolidone; (ii) One or more additional anionic monomers selected from the group consisting of: acrylic acid, methacrylic acid, sulfonic acid, phosphonic acid, and their alkali metal salts, alkaline earth metal salts, and ammonium salts, including but not limited to acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamidomethanesulfonic acid, acrylamidoethanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid; or Any combination of (iii)(i)-(ii); (c) One or more cationic glyoxalized polyacrylamide (GPAM) polymers, said one or more cationic GPAM polymers being obtainable by reacting glyoxal with one or more synthetic copolymers, terpolymers or quaternary copolymers of (a), one or more synthetic copolymers, terpolymers or quaternary copolymers of (b), or combinations thereof; (d) One or more semi-synthetic polymers comprising (a) or (b) the one or more synthetic copolymers, terpolymers, or quaternary copolymers optionally grafted onto one or more natural polymers, including but not limited to starch, chitin, chitosan, and natural polysaccharides; or Any combination of (e)(a)-(d), And the one or more cationic polymers said therein have a weight-average molecular weight in the range of 10,000-3,000,000 Da, 10,000-2,000,000 Da, 10,000-1,000,000 Da, 10,000-500,000 Da, 10,000-200,000 Da, 10,000-100,000 Da or 10,000-50,000 Da.

7. The method according to any one of claims 1 to 6, wherein the one or more cationic starches: (a) A cationic modified or unmodified starch comprising one or more of the following groups: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, rice starch, barley starch, pea starch, sweet potato starch, and any combination thereof; and (b) having a nitrogen content percentage (N%) ranging from 0.2-2%, 0.2-1.75%, 0.2-1.5%, 0.2-1.25%, 0.2-1% or 0.25-0.45% by mass, preferably 0.35-1.45% by mass.

8. The method according to any one of claims 1 to 7, wherein the one or more cationic starches are formulated by a method comprising the following steps prior to addition to the ASA sizing agent: (a) Dissolving dry cationic starch in water; cooking by methods including but not limited to spray cooking, steam cooking, or pot cooking; and cooling to a temperature in the range of 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, to obtain a cooked starch solution with a solid percentage in the range of 1-10%, 2-8%, or 3-6% by mass; or (b) Obtain a pregelatinized cationic starch with a solid percentage ranging from 20% to 40% by mass, and dilute it with water to obtain a pregelatinized starch solution with a solid percentage ranging from 1-10%, 2-8%, or 3-6% by mass.

9. The method according to any one of claims 1 to 8, wherein (i) the one or more cationic polymers are selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) quaternary copolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer, and (ii) the one or more cationic starches comprise corn starch, waxy corn starch, potato starch, cassava starch, wheat starch, or pea starch.

10. The method according to any one of claims 1 to 9, wherein the method comprises one or more of the following: (a) Adding the primary emulsifier to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and (b) Adding the secondary emulsifier to the primary emulsion to obtain a ratio of 0.25:1 to 2:

1. The mass ratio of dry starch to ASA is 0.3:1 to 1.6:1, 0.4:1 to 1.2:1, or 0.5:1 to 1:

1.

11. The method according to any one of claims 1 to 10, wherein the method comprises: (a) The primary emulsifier is added to the ASA sizing agent at ambient temperature and emulsified by stirring with an energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm; and / or (b) The secondary emulsifier is added to the primary emulsion at a temperature in the range of 20-80°C, 20-60°C, 20-40°C or 20-25°C, preferably 20-40°C, and emulsification is carried out by stirring with energy sufficient to achieve a median ASA particle size in the diameter range of 0.5-3 μm, 0.5-2 μm or 0.5-1 μm.

12. The method according to any one of claims 1 to 11, wherein the ASA sizing emulsion in its final form: (a) Includes median particle sizes with diameters ranging from 0.5–1 μm, 0.6–0.9 μm, or 0.7–0.8 μm; (b) Viscosities ranging from 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP, or 50-60 cP when measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C. (c) It exhibits stability over 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours, or 1-48 hours, wherein the stability is determined by the ASA sizing emulsion, and the ASA sizing emulsion retains... (i) The median particle size has a diameter of 0.5-3 μm, 0.5-2 μm, 0.5-1 μm, 0.6-0.9 μm or 0.7-0.8 μm, preferably less than 1 μm; (ii) When measured by a Brookfield viscometer with a No. 62 rotor at 60 rpm and 20 °C, the viscosity ranges from 10-100 cP, 20-90 cP, 30-80 cP, 40-70 cP or 50-60 cP, preferably less than 100 cP. (d) Add immediately to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp, or store in a tank or holding facility for 1-4 minutes, 1-10 minutes, 1 minute-1 hour, 1-6 hours, 1-12 hours, 1-24 hours or 1-48 hours before adding the ASA sizing emulsion to papermaking pulp, pulp or fiber raw material, optionally high-ash pulp; (e) Compared to ASA sizing emulsions prepared by a single or dual emulsification method using one or more emulsifiers containing one or more cationic starches, it contains a reduced final mass ratio of dry starch to ASA; or Any combination of (f)(a)-(e).

13. The method according to any one of claims 1 to 12, wherein when the stable alkenyl succinic anhydride (ASA) sizing emulsion is used as a sizing agent during the manufacture of the paper or paperboard, it produces a sheet product selected from the group consisting of: high ash paper or paperboard, printing or writing grade paper or paperboard, alkaline printing or writing grade paper or paperboard, bleached paper or paperboard, packaging grade paper or paperboard, and partially recycled or 100% recycled paper or paperboard, wherein the sheet product comprises optimal sizing performance as determined by industry-standardized testing, including but not limited to HST, Cobb, water droplet test, contact angle, edge wicking or water penetration, or combinations thereof, wherein the optimal sizing performance is determined relative to an equivalent sheet product comprising an ASA sizing emulsion prepared by a monoemulsification or doubulsification method using one or more emulsifiers comprising one or more cationic starches.

14. A dual-emulsification method for preparing alkenyl succinic anhydride (ASA) sizing emulsions for manufacturing paper and paperboard, the method comprising: (a) Obtaining or producing alkenyl succinic anhydride (ASA) sizing agent; (b) The ASA sizing agent is combined with a primary emulsifier and emulsified at ambient temperature, and stirred with energy sufficient to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming a primary emulsion; and (c) Following step (b), a secondary emulsifier is added and emulsified at a temperature ranging from 20-80°C, 20-60°C, 20-40°C, or 20-25°C, preferably 20-40°C, and stirred with sufficient energy to achieve a median ASA particle size ranging from 0.5-3 μm, 0.5-2 μm, or 0.5-1 μm in diameter, thereby forming the ASA sizing emulsion, and (d) Optionally, after step (c), the ASA sizing emulsion is added to the high-ash paper pulp. in (i) The primary emulsifier comprises an aqueous polymer solution containing an acrylamide cationic copolymer selected from the group consisting of: acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride copolymer (AMD / MAETAC), acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate (AMD / MAETAC / HEMA) terpolymer, acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2-hydroxyethyl methacrylate / acrylic acid (AMD / MAETAC / HEMA / AA) tetropolymer, and acrylamide / [2-(methacryloyloxy)ethyl]trimethylammonium chloride / 2,3-dihydroxypropyl methacrylate (AMD / MAETAC / DHPMA) terpolymer; (ii) The secondary emulsifier comprises one or more cationic modified or unmodified starches selected from the group consisting of: corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch, pea starch, and mixtures thereof; (iii) The high-ash paper pulp comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof; (iv) The high-ash paper pulp contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5%-25% by weight; (v) The primary emulsifier is added to the alkenyl succinic anhydride (ASA) sizing agent to obtain a ratio of the grams of active cationic polymer to the grams of ASA of 0.05:1 to 0.6:1, 0.1:1 to 0.5:1, 0.15:1 to 0.4:1, or 0.2:1 to 0.25:1; and (vi) The secondary emulsifier is added to the primary emulsion to obtain a dry starch to ASA mass ratio of 0.25:1 to 2:1, 0.3:1 to 1.6:1, 0.4:1 to 1.2:1 or 0.5:1 to 1:

1.

15. An ASA sizing emulsion composition or a papermaking pulp, pulp or fiber raw material comprising the ASA sizing emulsion composition, optionally a high-ash pulp, wherein the ASA sizing emulsion composition or papermaking pulp, pulp or fiber raw material can be obtained by the method according to any one of the preceding claims.

16. A method for producing paper or paperboard, the method comprising obtaining a high ash distribution pulp comprising wood pulp, optionally comprising a fiber raw material comprising a high content of recycled fiber and / or factory waste paper fiber, optionally a coarse fiber raw material, optionally a bleached fiber raw material, optionally containing process water from pulp, paper, or paperboard production; and treating the fiber raw material at the wet end of a paper machine with an ASA sizing emulsion according to any one of the preceding claims, wherein: (a) The high-ash slurry comprises ash selected from the group consisting of: calcium carbonate, TiO2, kaolin, silicates, carbonate-based pigments, kaolin-based pigments, or any combination thereof; and (b) The high ash content slurry contains 1-35%, 2-30%, 5-25% or 10-20% ash content by weight, preferably 5%-25% ash by weight.

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