Treated substrates and methods for their production

Abstract

The present invention provides a treated substrate and methods of forming the same. In one exemplary embodiment, the treated substrate comprises lignocellulose and a polymer fixed to the lignocellulose to form the treated substrate. The polymer comprises a succinic moiety capable of reversibly changing between succinic anhydride and succinic acid moieties. The treated substrate has a wet tensile index of about 3 Newton-meters per gram or less.

Description

[0001] Priority requirements

[0002] This application claims the benefits of U.S. Non-Provisional Application No. 17 / 647,861, filed January 13, 2022, and U.S. Provisional Application No. 63 / 138,882, filed January 19, 2021, which are incorporated herein by reference. Technical Field

[0003] This application relates to treated substrates and methods of producing them, and more specifically to lignocellulosic substrates treated with polymer compounds for use in the pulp and paper industry. Background Technology

[0004] Since the earliest days of the modern pulp and paper industry, efforts have been made to expand the performance potential of wood pulp fibers by attaching ionizable carboxylic acid groups to the exposed fiber surfaces. These efforts were inspired by the understanding that the presence of ionized carboxyl groups promotes increased swelling and flexibility of cellulose fibers during papermaking, reduced keratinization, increased ion exchange capacity, and increased adsorption capacity and strength. The resulting paper can be a better absorbent and is stronger both wet and dry.

[0005] By definition, pure cellulose does not contain carboxylic acid groups. In contrast, wood pulp fibers have some ionized groups (usually carboxyl groups) due to the presence of hemicellulose and lignin. The total fiber charge content is typically expressed as the equivalent of titratable groups per (gram) of dry fiber mass, expressed as a positive number, although the charge is mostly negative. Ionizable carboxylic acid groups are titratable and can therefore be measured. Bleached kraft pulp has a low charge content, approximately 0.01 milliequivalents (meq / g) per gram of dry fiber. Unbleached and chemithermomechanical pulp (CTMP pulp) typically has a titratable charge an order of magnitude higher. The topochemical distribution of charge within pulp fibers is typically characterized by two values: "total charge" and "surface charge." Total charge can be measured by conductivity titration or by the adsorption of very low molecular weight cationic polymers. Surface charge is determined by the adsorption of high molecular weight cationic polymers that cannot penetrate the pores in the pulp fiber walls.

[0006] Two common methods for introducing carboxyl groups onto and into pulp fibers are: 1) oxidation to obtain carboxylic acid groups; and 2) covalent grafting of charged molecules. The carboxymethylation of cellulose in isopropanol with monochloroacetic acid is a good example of the covalent bonding of charged small molecules, frequently described in the literature. Neither oxidation nor small molecule grafting is suitable for implementation in conventional pulp mills because they involve potentially polluting and expensive low-molecular-weight organic solvents and / or reagents.

[0007] Another method to increase the surface charge of fibers is by attaching charged polymers. Although polymers can be grown on the fiber surface—a process known as "grafting"—this method involves small-molecule organic chemistry and is not suitable for pulp mill applications. Surface charge enhancement can provide stronger fiber / fiber bonding, increased ion exchange capacity, increased water absorption, and increased functional groups for subsequent surface modification. Despite these potential advantages, kraft pulp with enhanced surface properties is not widely available because bleached cellulose fibers have a non-beneficial, relatively inactive surface that is difficult to chemically modify under the moisture conditions of pulp mills.

[0008] Surface-modified pulp should be suitable for papermaking processes. When added to water, bundles of commercially available dry pulp should readily disperse into individual fibers—a process known in the papermaking industry as repulping. For treated pulp, polymer-reinforced fiber / fiber bonding can impart high wet strength to the dry pulp, thus deterring rapid repulping in paper mills. For example, both patent US 6,579,415 B2 (Jewell, RAMethod of Increasing the Wet Strength of a Fibrous Sheet, June 17, 2003) and scientific literature (Xu, GG; Yang, CQ; Deng, Y. Effects of Poly(vinyl Alcohol) on the Strength of Kraft Paper Crosslinked by a Polycarboxylic Acid. J. Pulp Paper Sci. 2001, 27, 14-17; Yang, CQ; Xu, Y.; Wang, D. FT-IR Spectroscopy Study of the Polycarboxylic Acids Used for Paper Wet Strength Improvement. Ind. Eng. Chem. Res. 1996, 35, 4037-4042) report that maleic anhydride copolymers impart high wet strength. This literature indicates that such treatment results in products that are difficult to re-pulp. Pulp with a wet tensile index of about 3 N·m / g or higher is difficult to re-pulpify, while pulp with a lower wet tensile index is more suitable for rapid dispersion in a pulper prior to the papermaking process. The term "pulp" can refer to both the dried product and a wet suspension without a wet tensile index. Pulp sheets formed during laboratory papermaking processes do indeed have a wet tensile index.

[0009] Therefore, treated substrates and methods for treating such substrates to produce lignocellulose with increased surface charge are desirable. Furthermore, treated substrates with a wet tensile index of about 3 N·m / g or less should be suitable for papermaking processes. In addition, other desirable features and characteristics will become apparent from the following detailed description and appended claims, taken in conjunction with the accompanying drawings and this background art. Summary of the Invention

[0010] A treated substrate and a method for forming the same are provided. In one exemplary embodiment, the treated substrate comprises lignocellulose and a polymer fixed to the lignocellulose to form the treated substrate. The polymer comprises a succinic acid moiety capable of reversibly varying between succinic anhydride and succinic acid moieties. The treated substrate has a wet tensile index of about 3 N·m / g or less.

[0011] In another embodiment, the treated substrate comprises lignocellulose and a polymer fixed to the lignocellulose to form the treated substrate. The polymer includes poly(ethylene-co-maleic acid), and the treated substrate has a wet tensile index of about 3 N·m / g or less. The treated substrate has a fixed γ. f The value represents the amount of polymer fixed to the treated substrate, measured in milliequivalents of titratable carboxyl groups per gram of dry treated substrate polymer. This fixed Γ value is approximately 0.001 milliequivalents or greater per gram of dry treated substrate.

[0012] In yet another embodiment, a method for forming a treated substrate is provided. The method includes applying a polymeric component to an untreated substrate to form a polymeric substrate assembly. The untreated substrate comprises lignocellulose, and the polymeric component comprises a polymer having a succinic acid moiety capable of reversibly varying between succinic anhydride and succinic acid moieties. The polymer is fixed to the untreated substrate by heating the polymeric substrate assembly to a curing temperature of approximately 100°C or higher and maintaining this curing time to form the treated substrate. Heating of the polymeric substrate assembly is terminated when the wet tensile index of the treated substrate is approximately 3 N·m / g or less, and when the fixed Γ value of the treated substrate is approximately 0.001 milliequivalents or greater per gram of dry treated substrate. The fixed Γ value represents the amount of polymer fixed to the treated substrate, measured in milliequivalents of titratable carboxyl groups per gram of dry treated substrate polymer. Attached Figure Description

[0013] The present disclosure will now be described with reference to the accompanying drawings, wherein the same numerals denote the same elements, and:

[0014] Figure 1 and Figure 2These are different embodiments of methods for producing treated substrates and schematic diagrams of the treated substrates; and

[0015] Figure 3-11 The diagram shows the experimental results of various aspects and factors that affect the results of this disclosure. Detailed Implementation

[0016] The following detailed description is merely exemplary in nature and is not intended to limit the application or use of the described embodiments. Furthermore, it is not intended to be bound by any theories set forth in the foregoing technical field, background art, summary of the invention, or the following detailed description.

[0017] Untreated cellulose substrates are treated with polymers containing succinic acid moieties to provide chargeable surface carboxylic acid moieties. The polymer component is applied to the untreated substrate, and the polymer is fixed to lignocellulose by heating to produce a treated substrate. The treated substrate with the fixed polymer is at least partially dried during the curing process. The polymer is fixed to lignocellulose, wherein the polymer can be covalently bonded to the lignocellulose via ester bonds or physically adhered to it, such that the polymer is retained along with the lignocellulose in subsequent processing and increases the strength of paper made from the treated substrate. However, treated cellulose substrates tend to have high wet tensile index, making repulping of the dried treated substrate difficult. Without being bound by theory, but presumably, the process conditions for fixing the polymer to the treated substrate are also used to convert the succinic acid moieties from the succinic acid form to the succinic anhydride form, or to crosslink the fixed polymer to form an inter-fiber crosslinking network at fiber-to-fiber contact points. It has been found that if the curing process is controlled, the polymer can be fixed to lignocellulose while limiting the increase in the wet tensile index, thus avoiding a large-scale conversion of the succinic acid form to the succinic anhydride form. In various implementations, a number of different device configurations can be used to fix the polymer to the substrate, thereby determining a measurable parameter indicating the heating conditions that provided a high fixation yield and an acceptablely low wet tensile index during the curing process. This measurable parameter is the βΓ product of the treated substrate (βΓ). a (This will be defined more fully in the following disclosure).

[0018] refer to Figure 1The untreated substrate 10 comprises lignocellulose, which may include cellulose, hemicellulose, lignin, and other materials. Lignocellulose is a plant biomass. In one exemplary embodiment, the untreated substrate 10 primarily comprises wood pulp, and in some embodiments may comprise kraft pulp. As used herein, the term "primarily comprises" means that the specified component constitutes about 50% by weight or more of the specified material based on the total weight of the specified material. In one exemplary embodiment, the untreated substrate 10 is a raw material for papermaking and may be formed from wood, cotton, or other fiber crops, or other materials known to provide pulp suitable for papermaking processes. In one exemplary embodiment, the untreated substrate 10 may comprise about 25% to about 100% by weight of lignocellulose based on the total weight of the dried untreated substrate 10. In various embodiments, other materials may also be present in the untreated substrate 10.

[0019] In one exemplary embodiment, polymer component 12 and untreated substrate 10 are combined in polymer application process 20 to form polymer substrate assembly 8. Polymer component 12 may be as follows: Figure 2 The exemplary embodiments shown are performed using a dry method or as follows Figure 1 As shown in the exemplary implementation and continuing to refer to Figure 2 The polymer component 12 is applied to the untreated substrate 10 using a wet process. In a dry process, a limited amount of polymer component 12 is added to the untreated substrate 10 such that the water content remains low, for example, less than about 75% based on the dry weight of the untreated substrate. Some embodiments that can utilize the dry treatment process include coating application processes, applicator application, or spraying.

[0020] In an alternative embodiment, polymer component 12 is added to untreated substrate 10 in a wet process to form polymer substrate assembly 8, wherein the untreated substrate 10 and polymer component 12 comprise a significant amount of water. Some exemplary embodiments utilizing the wet process include a pulp dryer headbox, a pulp tank, or a pulp stream entering a pipe. Generally, during the polymer application process 20, the amount of water in polymer substrate assembly 8 can vary from about 0% to about 99.9% based on the weight of polymer substrate assembly 8 (including any water present in polymer substrate assembly 8). The amount of water present in polymer substrate assembly 8 is not significant.

[0021] Polymer component 12 comprises a polymer and, in various embodiments, may include water and other materials. In a wet process, the untreated substrate 10 may be dehydrated, for example, by filtration or centrifugation, before proceeding further. Polymer component 12 may be added to the untreated substrate 10 as a solution in the presence of water, but in alternative embodiments it may also be added as a solid or high-concentration polymer. The pH of the polymer substrate assembly 8 is adjusted with a suitable acid and / or base, such as hydrochloric acid, sulfuric acid, and / or sodium hydroxide. In some embodiments, an acid and / or base may be added to polymer component 12, or in alternative embodiments, an acid and / or base may be added to the untreated substrate 10 or otherwise added to polymer substrate assembly 8. In one exemplary embodiment, polymer component 12 comprises about 2% by weight of polymer based on the total weight of polymer component 12, wherein water is the major component of the polymer component (i.e., exceeding about 50% by weight of polymer component 12). However, in alternative embodiments, a variety of different concentrations of polymer in polymer component 12 may be used, as long as at least some polymer is present. For example, polymer component 12 may include about 0.1 to about 100% by weight of polymer or about 0.3 to about 50% by weight of polymer, or may include other concentrations of polymer in various embodiments. Solvents other than water may also be used, or solvents other than water may be used, such as acetone, ethanol, methanol, or a variety of other solvents. When the polymer is present in the polymer matrix assembly 8, the polymer may be hydrolyzed, as explained in more detail below.

[0022] The polymer in polymer component 12 contains a succinic acid moiety. This succinic acid moiety can reversibly change between a succinic anhydride moiety and a succinic acid moiety. The succinic acid moiety (commonly referred to as the "acid") comprises two carboxylic acid moieties that react with each other to form an anhydride. These two carboxylic acid moieties are separated from each other by two atoms in the succinic acid moiety, where these two atoms are carbon atoms. The anhydride is... The succinic anhydride moiety is in the form of C(=O)OX, where X is a hydrogen atom or a compound ionically bonded to a C(=O)O group, such as chloride, sulfate, potassium, or other cations. Therefore, the terms "succinic anhydride moiety" and "carboxylic acid moiety" include acidic forms where X is a hydrogen atom, and also include carboxylates where X is a cation other than hydrogen. The succinic anhydride moiety includes a titratable carboxyl group, wherein the succinic anhydride moiety or succinic acid moiety includes two titratable carboxyl groups, and the carboxylic acid moiety includes one titratable carboxyl group. Therefore, the total titratable carboxyl groups of the polymer include (i) the two carboxyl groups of the succinic anhydride moiety, (ii) the two carboxylic acid moiety portions of the succinic acid moiety, and (iii) the sum of any titratable carboxylic acid moiety portions of the polymer that are not part of the succinic anhydride moiety or succinic acid moiety.

[0023] In some embodiments, the polymer may have a weight-average molecular weight of about 1 to about 100,000 kilodaltons or greater. In one exemplary embodiment, the polymer has a weight-average molecular weight of about 2 to about 10,000 kilodaltons, but in an alternative embodiment, the polymer has a weight-average molecular weight of about 20 to about 100 kilodaltons. However, other weight-average molecular weights may be used in alternative embodiments.

[0024] In one exemplary embodiment, the polymer is a copolymer formed from maleic anhydride or maleic acid and another compound to be polymerized with maleic anhydride or maleic acid. The other compound may include double bonds, such as olefins, and may include other functional groups, such as acrylic acids, methacrylic acids, or other compounds. For example, the polymer may be a copolymer of maleic anhydride, maleic acid, or combinations thereof with monomers selected from: acrylic acid, methacrylic acid, styrene sulfonic acid, vinyl sulfonic acid, acryloylaminomethylpropane sulfonic acid, diallyl dimethylammonium salt, acryloylethyl trimethylammonium salt, acryloylethyl dimethylamine, ethylacryloylethyl trimethylammonium salt, ethylacryloylethyl dimethylamine, methacryloylethyl trimethylammonium salt, methacryloylethyl dimethylamine, acryloylaminopropyl trimethylammonium salt, acryloylaminopropyl dimethylamine, methacryloylaminopropyl trimethylammonium salt, methacryloylaminopropyl dimethylamine, vinylformamide, vinylamine, acrylamide, methacrylamide, N-alkylacrylamide, vinylformamide, ethylene, methyl vinyl ether, octadecene, styrene, isobutylene, and mixtures thereof.

[0025] In one exemplary embodiment, the polymer comprises a poly(ethylene-co-maleic acid) compound, wherein the term "maleic acid," when used in the name of the polymer, refers to the portion that can be reversibly changed between a succinic acid moiety and a succinic anhydride moiety. Maleic acid groups may provide the polymer with succinic acid moieties such as succinic anhydride and / or succinic acid moieties, and other comonomers may optionally provide succinic acid moieties and / or carboxylic acid moieties on the polymer. In one exemplary embodiment, the polymer comprises poly(ethylene-co-maleic acid), poly(butadiene-co-maleic acid), and combinations thereof. In an alternative embodiment, the polymer comprises poly(ethylene-co-maleic acid).

[0026] In one exemplary embodiment, the polymer substrate assembly 8 is adjusted to a pH of about 4. In different exemplary embodiments, the polymer substrate assembly 8 may be adjusted to a pH of about 2 to about 5, or a pH of about 3 to about 4.5, or a pH of about 3.5 to about 4.5. A low pH value (value less than about 5) ensures that at least some of the succinic acid fractions include succinic acid fractions, which can facilitate reaction with the hydroxyl fractions of lignocellulose to form ester bonds. In some embodiments, the pH of the polymer substrate assembly 8 is adjusted by adjusting the pH of polymer component 12, wherein polymer component 12 is applied as an aqueous solution. In some embodiments, the polymer substrate assembly 8 is catalyst-free. Specific catalysts that may be absent (i.e., can be excluded) include, but are not limited to, alkali metal hypophosphites and phosphites (i.e., MH2PO2, MH2PO3, and M2HPO3), where M is an alkali metal; alkali metal salts of polyphosphoric acids; lithium dihydrogen phosphate; sodium dihydrogen phosphate; potassium dihydrogen phosphate; sodium hypophosphite; sodium salts of dichloroacetic acid; p-toluenesulfonic acid; 1,4-dimethylaminopyridine; 1-methylimidazole; and combinations thereof. As used herein, the term “absent” means that the specified component is present at a concentration of 0.01% by weight or less based on the total weight of the specified composition (i.e., polymer substrate composition 8).

[0027] Still referencing Figure 1 and 2 In the curing process 22, the polymer is fixed to the untreated substrate 10 to form the treated substrate 14. Not bound by theory, but in one exemplary embodiment, it is assumed that at least some of the polymers form ester bonds with lignocellulose, wherein the succinic anhydride of the polymer reacts with the hydroxyl groups of the lignocellulose to form ester bonds. Some polymers may also be physically fixed rather than covalently bonded to the treated substrate 14. Even after stirring and soaking for two days, physically fixed polymers will not be washed out of the treated substrate 14 into the aqueous solution. Thus, any physically fixed but possibly not covalently bonded polymers to the treated substrate 14 are retained with the treated substrate 14 during subsequent processing, and the paper made from the treated substrate 14 exhibits the benefits of the polymer. Not bound by theory, but assuming that substantially all polymers are covalently bonded to the treated substrate 14, and that physical fixation may be a negligible factor. The amount of polymer present can be expressed as “added polymer,” which includes the total amount of polymer added to the untreated substrate 10, and can be referred to as added Г(Г). a The "fixed polymer," that is, the amount of polymer fixed onto the treated substrate 14, can be referred to as the fixed Г(Г). f The amount of fixed polymer divided by the amount of added polymer (Г). f / Г a The fixed yield of the curing process 22 was obtained.

[0028] The curing process 22 includes applying heat to the untreated substrate 10, which is wetted with polymer component 12. In one exemplary embodiment, the untreated substrate 10 and polymer component 12 are heated to a curing temperature 16 of at least about 100 degrees Celsius (°C) for a curing time 18. In alternative embodiments, the untreated substrate 10 and polymer component 12 are heated to a curing temperature 16 of about 120°C to about 500°C, or a temperature of about 150°C to about 400°C, or a temperature of about 180°C to about 300°C. The untreated substrate 10 and polymer component 12 are exposed to the curing temperature 16 for a curing time 18 sufficient to fix the polymer to the treated substrate 14, but wherein the curing time 18 is short enough to keep the wet tensile index below a desired value, as described more fully below. In some embodiments, the curing process 22 may be a multi-step curing process 22 involving two or more separate heating processes (not shown), wherein the untreated substrate 10 and polymer component 12 are heated in a first step and then reheated in a subsequent step.

[0029] The “wet tensile index” of the treated substrate 14 mentioned herein refers to the wet tensile index of handmade paper formed from the treated substrate 14, wherein the mass of the dry handmade paper comprises at least about 90% by weight of the treated substrate 14, based on the weight of the dry treated substrate 14. The wet tensile index measurement result used herein is defined as the wet tensile index of handmade paper; therefore, directly measuring the treated substrate 14 in forms other than handmade paper is not applicable. Handmade paper can be formed by various methods, among which exemplary methods are described in the “Examples” section below. Therefore, the term “wet tensile index” of the treated substrate 14 is equivalent to the wet tensile index of the handmade paper formed from the treated substrate 14.

[0030] The product of βΓ of the treated substrate (βΓ) a ) can be used to determine the appropriate curing time 18, but βГ a The expected value varies with different types of untreated substrates 10 and different types of polymers. In addition to the type of untreated substrate 10 and polymer, the curing time 18 will also vary with many other factors, including but not limited to the thickness of the untreated substrate 10 when exposed to the curing temperature 16, the amount of water absorbed by the untreated substrate 10, the amount of water freely mixed with the untreated substrate 10, the rate at which the temperature rises to the curing temperature 16, the type of equipment used, and other variables. The curing time 18 will be limited because the longer the exposure time, the greater the wet tensile index and the larger the βΓ product.

[0031] An exemplary curing time 18 may be from about 30 seconds to about 2 hours, or from about 30 seconds to about 1 hour, or from about 1 minute to about 30 minutes, or from about 1 minute to about 15 minutes, or from about 1 minute to about 10 minutes. The curing time 18 includes the sum of the heating periods in each heating process of the multi-step curing process 22. Once the heat source is removed, residual heat in the treated substrate 14 may contribute to further curing, and this residual heat should be included in the time used to determine βΓ. a In the process calculations. In an exemplary embodiment applicable to an industrial papermaking process, the curing time 18 can be the time the wet pulp is in the drying section of a pulp dryer. The polymer component 12 can be applied to the untreated substrate 10 before, during, or after the drying section of the pulp dryer. The residence time and / or temperature in the drying section can be adjusted to provide satisfactory sufficient curing and wet tensile index. The product of βΓ and the wet tensile index corresponding to 3 N·m / g of treated substrate for the desired type of pulp and desired polymer can be determined in the laboratory. a3 ), as described more fully below, in which βГ a3 This can guide the determination of residence time and temperature in the drying section. The processing may include other techniques as a supplement to or alternative to the drying section, wherein the untreated substrate 10 may be exposed to an infrared dryer, a heating furnace, or other techniques that apply heat to the untreated substrate 10 and the polymer component 12.

[0032] While not bound by theory, it is hypothesized that as curing time 18 progresses, the succinic acid portion transforms into the succinic anhydride portion, thus longer exposure leads to more succinic acid portion transforming into the succinic anhydride portion. A longer curing time 18 may also generate more covalent bonds linking the polymer, or other mechanisms. In any case, the desired wet tensile index level is achieved by controlling and terminating the curing process 22 before the wet tensile index increases too much (such as reaching a level greater than about 3 N·m / g).

[0033] Fixed Г(Г) fThe value represents the amount of polymer immobilized to the treated substrate 14 and is measured in milliequivalents (meq / g) of titratable carboxyl groups per gram of dry treated substrate polymer. All carboxylic acids and anhydrides are titratable, with the succinic anhydride moiety converting to the succinic acid moiety upon exposure to water. Anhydrides have a short lifetime in water as they quickly revert to acids; therefore, all carboxylic acid and anhydride groups are measured as described above during titration. The treated substrate 14 is titrated to measure the titratable carboxyl groups; therefore, the initial titration includes a combination of titratable carboxyl groups attributed to the polymer and any titratable carboxyl groups attributed to the untreated substrate 10. The amount of titratable carboxyl groups on the untreated substrate 10 is measured before the start of the treatment process, and this value is subtracted from the amount of titratable carboxyl groups found after the treatment process to determine the amount of polymer immobilized to the treated substrate 14, in milliequivalents (meq / g) of dry treated substrate 14. polymers The titrability of carboxyl groups can be measured by milliequivalent titration. The milliequivalent titration of carboxyl groups can be measured by conductivity titration. The treated substrate 14 can be washed prior to titration to remove any remaining unfixed polymer in the treated substrate 14.

[0034] To convert the polymer's meq / g to the mass of an exemplary polymer, such as grams per gram of dry pulp poly(ethylene-co-maleic anhydride) (PEMA), multiply the meq / g by the polymer's carbonyl equivalent weight, which is 63.05 Daltons for PEMA. The treated substrate 14 should have a specific minimum amount of polymer immobilized thereon to provide the desired available carboxylic acid groups. Therefore, the immobilized Γ(Γ) f The value should be at least approximately 0.001 meq / g, such as Г f The value is approximately 0.001 to approximately 4 meq / g. In an alternative embodiment, the Γ of the treated substrate 14... f The value is approximately 0.001 to approximately 1 meq / g, or approximately 0.005 to approximately 0.5 meq / g.

[0035] The wet tensile index of the treated substrate 14 is measured. In one exemplary embodiment, the wet tensile index is measured using the Tappi standard wet tensile index test, such as the TAPPI methods T456 om-10 and / or T494 om-96. Other wet tensile index tests may also be used in alternative embodiments, such as modified TAPPI methods, such as changing the test strip size for the number of repetitions. In one exemplary embodiment, the wet tensile index of the treated substrate 14 is from about 0 to about 3 Newton-meters per gram (Nm / g). Reference to the wet tensile index of the treated substrate 14 refers to the wet tensile index of the handmade paper prepared from the treated substrate 14 as described above. Experience shows that if the wet tensile index is about 3 Nm / g or less, the treated substrate 14 can be re-pulped with minimal effort, but if the wet tensile index is higher than about 3 Nm / g, the re-pulping effort becomes prohibitive. However, if the wet tensile index is about 2.5 Nm / g or less, the treated substrate 14 is more easily repulped, and even more so if the wet tensile index is about 2 Nm / g or less. Therefore, in alternative embodiments, the wet tensile index of the treated substrate 14 may be about 0.5 to about 2.5 Nm / g, or about 0.5 to about 2.2 Nm / g or less, or about 0.5 to about 2 Nm / g. The ease with which the treated substrate 14 can be repulped can result in lower papermaking costs because repulping requires less time and effort.

[0036] β(β) is the fraction of succinic acid portion that has been converted to the succinic anhydride portion, a conversion that may occur during curing. It has been proposed that β is a good, simple measure of the progress of curing during the treatment process. The β value is a dimensionless fractional value from 0 to 1. The method used to estimate β is described in the Examples section below. It is difficult to actually measure the quotient of the number of succinic anhydride portions to the total number of succinic acid portions. The β value has been estimated using a model for the results presented herein, as explained in the Examples section below, where the results are calculated using reaction rates. The β value represents only the succinic acid portion converted to the form of succinic anhydride and does not include any carboxylic acid portions present in the treated substrate 14 that are not part of the succinic acid portion, such as any carboxylic acid portions present on hemicellulose or otherwise present in the untreated substrate 10, or any carboxylic acid portions on the polymer that are not part of the succinic acid portion. This would include carboxylic acid portions on polymers such as those from acrylic copolymers. Any carboxylic acid portions present in the treated substrate 14 that are not part of the succinic acid portion are subtracted or removed from the calculated β value.

[0037] It has been shown that the wet tensile index is related to the product of the βΓ of the treated substrate (βΓ). a ) related, of which βГ a It is the value of β (without units) multiplied by Г aThe result of the value, where Г a The values ​​are measured in meq / g as described above. This βГ a The wet strength of the treated substrate 14 is related to the contribution of (i) the amount of polymer added and (ii) the degree of curing of the polymer and the treated substrate 14. The wet strength of the treated substrate 14 is measured and discussed herein as the wet tensile index. If βГ a If the product becomes too high, the wet tensile index increases and the treated substrate 14 becomes difficult to re-pulp. In the following examples section, the wet tensile index of pulp treated dry has been measured, but the results apply to pulp treated wet; therefore, βГ a The product indicates that the pulp is repulpable regardless of the treatment method used. The curing process 22 requires heat, therefore, at the end of the curing process 22, the treated substrate 14 is dried to a certain extent as water is evaporated and / or boiled away. βГ is expressed in the above units. a The value can be determined in the laboratory, and this simplifies the determination of variables in the curing process 22, which produces a treated substrate 14 with a sufficiently low wet tensile index.

[0038] In one exemplary implementation, βГ is determined for a range of curing conditions. a The product of β and Γ of the wet tensile index of the treated substrate 14 corresponding to 3 N·m / g of the treated substrate (βΓ) a3 The βΓ of the treated substrate in the form of laboratory handmade paper, corresponding to a wet tensile index of 3 Nm / g, can be measured as described above. a (in meq / g) to determine. Therefore, βГ a3 The conditions for curing process 22 are predicted to result in a wet tensile index of 3 Nm / g. In alternative embodiments, alternative βΓ products can be determined for other desired maximum wet tensile indexes (e.g., 2 Nm / g). βΓ can be determined for various combinations of pulp and polymer. a3 The laboratory-determined results (or any other βГ product used as an alternative to the desired wet tensile index).

[0039] The combination of a robust, untreated substrate 10 and a high molecular weight polymer tends to have a high fixed yield, therefore controlling the curing time 18 and curing temperature 16 to limit the β value helps to reduce the wet tensile index and the corresponding βΓ. a Limit to below the desired value. For low molecular weight polymers, the fixed yield tends to be low, therefore controlling the curing time 18 and curing temperature 16 helps to improve the fixed yield. βГ a Product is an effective method for balancing the competitive challenges of polymers with different molecular weights.

[0040] The following experimental data are provided to demonstrate the details of this disclosure. Please refer to [link / reference needed]. Figure 1 and 2 Come and check Figure 3-1 The chart in 2.

[0041] Example

[0042] Material. Poly(ethylene-co-maleic anhydride) (PEMA, Mw 100-500kDa) repurchased from E60 (PEMAMw 60kDa) is manufactured in the United States. Offered. Never-dried, bleached northern cork from... Provided. TAPPI standard blotting paper was purchased from Labtech Instruments, Canada. TM Inc. All other chemicals were purchased from [unclear - likely a company name].

[0043] pH testing of polymer component 12 during the treatment of untreated substrate 10 showed that pH had a significant effect on the retention of polymer in the treated substrate 14.

[0044] Polyanhydride hydrolysis. Polyanhydride copolymers are hydrolyzed to the corresponding polybasic acids. In a typical hydrolysis experiment, 1 gram of poly(ethylene-co-maleic anhydride) (sometimes referred to herein as PEMA) powder is dispersed in 49 grams (g) of a 1 millimolecular (mM) sodium chloride (NaCl) solution. Most of the experiments in this paper were conducted in diluted salt to control the ionic strength. After 2 days, the poly(ethylene-co-maleic anhydride) (PEMAc) solution was clear.

[0045] Preparation of handmade paper. Preparation of pulp sheets for polymer treatment (75 g / m²). 2) The pulp flakes are made from bleached pulp (15g, dry weight) that has never been dried: diluted to 2 liters (L) with deionized water and processed in a British shredder. Grind in an Instruments Inc. (model 500-1) machine (15,000 rpm). Add 200 ml (mL) of 0.75% pulp to a semi-automatic paper forming machine. In Instruments Inc., model 300-1, the pulp is further diluted to 0.019% with deionized water and then dewatered. The wet handmade paper is pressed between suction pads at a pressure of 635 kPa for 5 minutes at room temperature (approximately 23°C) (Standard Auto CH Benchtop Press). Inc., US). The pressed sheet was placed in a drying ring to dry overnight at 50% relative humidity and 23°C.

[0046] Pulp treatment. In a typical treatment experiment, 3 mL of a 2% by weight PEMAc solution with the desired pH value is added dropwise to dry pulp sheets (approximately 1.5 g, 75 g / m³) over approximately 2 minutes. 2 The entire surface of the wet pulp sheet is then covered. The wet pulp sheet is then placed between two absorbent sheets and rolled twice using a standard brass tumbler roll (102 mm in diameter and 13 kg in weight) from the Technical Association of Pulp and Paper Industry (TAPPI) to remove excess polymer component.12 The sheet is weighed before and after processing to calculate the mass of polymer applied. The processed sheet between the two absorbent sheets is then placed in a rapid dryer. On Instruments Inc., it is cured at a curing temperature of 16 and a curing time of 18, such as curing at 120°C for 10 minutes.

[0047] The amount of polymer that can be washed off the pulp is measured to estimate the amount of polymer remaining fixed to the fibers. Specifically, pulp sheets are placed in 200 mL of 1 mM NaCl solution in a 250 mL beaker. While not bound by theory, the carboxyl groups of the polymer can react with the hydroxyl groups of the ester to form covalent ester bonds between the polymer and the treated substrate 14. Some polymers can also be physically fixed to the treated substrate 14 where no covalent chemical bond exists between the polymer and the treated substrate 14; however, the polymer can adhere to or otherwise physically attach to the treated substrate 14 without covalent bonds. After stirring with a magnetic stir bar for 30 minutes, the pulp is filtered to separate the fibers, and the polymer content in the washing solution is measured by conductivity titration. The washing procedure is repeated to ensure that no polymer remains in the second washing solution.

[0048] Washing is used to determine the fixation yield. The amount of polymer that can be washed off the pulp is measured to estimate the amount of polymer retained fixed on the fibers. Specifically, pulp flakes are torn into small pieces and added to 200 mL of 1 mM NaCl solution in a 250 mL beaker. After stirring with a magnetic stir bar for 30 minutes, the pulp is filtered to separate the fibers. The washing procedure is repeated. The polymer content of the washing solution is measured to calculate the PEMAc bonding yield based on the washing solution. The PEMAc content of the fibers is also measured directly by conductivity titration. At higher wet strengths, [the following method is used]. Baby The blender repulpers the pulp sheets, and then a standard shredder (30,000 rpm) is used to separate the pulp into individual fibers.

[0049] Polyelectrolyte titration was used to measure the amount of PEMAc immobilized on the surface of the outer fibers. Approximately 0.1 g of dry weight of wet, washed PEMAc-grafted pulp was added to 40 mL of poly(diallyldimethylammonium chloride) (PDADMAC) (1.177 meq / L) in 1 mM NaCl. The suspension was mixed with a magnetic stir bar at pH 10 for 30 minutes to promote PDADMAC adsorption. The suspension was then placed in a container... Filter the solution through a 4.7 cm Buchner funnel using qualitative filter paper. The concentration of unabsorbed PDADMAC in the filtrate was determined by titration with potassium polyvinyl sulfate (PVSK) (1 meq / L). The PCD-03 particle charge detector determines the endpoint. The charge of the initial cellulose substrate is subtracted to determine the amount of fixed PEMAc.

[0050] Measure wet strength. Cut a paper sample (1.5cm × 14cm) from the prepared paper and then soak it in 1mM NaCl for 5 minutes before testing. Remove excess water by gently pressing between two sheets of absorbent paper. Use a 50-Newton load cell. 4411 General Testing System ( Corporation, Canton, MA) typically follows the TAPPI methods T46 om-10 and T494 om-96 to measure tensile strength. The crosshead speed is 25 mm / min. At least three measurements are taken for each type of paper.

[0051] Quantitative determination of PEMAc: Conductometric titration was used to measure the concentration of PEMAc in solution and on pulp fibers. 90 mL of 4 mM NaCl solution was added to a wet pulp sample (dry weight 0.2 g). The initial pH was adjusted to below 3.0 by adding 1 M hydrochloric acid (HCl). 0.1 M NaOH solution was added at a rate of 0.05 mL / min using an automated titrator (MANTECH, benchtop titrator model MT-10) until the pH reached 11.5. The titration was repeated at least three times with fresh samples. The volume of base consumed by the weak carboxyl group was determined by the intersection of three trend lines that traverse the linear region of the titration curve, such as... Figure 3 As shown in the example.

[0052] Figure 4 and 5 The dependence of constant yield on the pH, curing temperature 16, and molecular weight of the polymer component 12 of the treatment agent is shown. H-PEMAc refers to high molecular weight poly(ethylene-co-maleic acid) with a molecular weight of about 100 to about 500 kilodaltons (kDa), and L-PEMAc refers to low molecular weight poly(ethylene-co-maleic acid) with a molecular weight of about 60 kDa. Figure 4The treatment yield of pulp sheets cured at 23°C for more than 12 hours is shown as a function of the pH of the treatment solution and the molecular weight of PEMAc. At this temperature, the succinic acid fraction is expected not to be chemically converted to the succinic anhydride fraction. Physical fixation is the only operational mechanism. The fixation yield of H-PEMAc (100-500 kDa) is approximately 50% at pH 2-11, peaking at approximately 70% at pH 4. In the experimental data graph, H-PEMAc is shown as square data points, and L-PEMAc is shown as circular data points. Figure 5 The corresponding fixation yields for pulp cured at 120°C for approximately 10 minutes are shown. Note that the high-yield samples could not be re-pulped for titration; therefore, the yields are based on wash water measurements. When the treatment solution was acidic, the yields were high and independent of the PEMAc molecular weight, indicating chemical curing. However, when using an alkaline solution, the H-PEMAc yield level was approximately 0.4 due to physical fixation, while no L-PEMAc residue remained on the washed pulp.

[0053] The effects of curing time and temperature. Figure 6 and Figure 7 The effects of curing time 18, curing temperature 16, and PEMAc molecular weight on the PEMAc content of the washed fibers are shown. Figure 6 A constant curing temperature of approximately 120°C is shown for 16, with the curing time 18 shown on the X-axis. Figure 7 A constant curing time of 10 minutes is shown, with the curing temperature 16 indicated on the X-axis. The curing of H-PEMAc is shown at... Figure 6 and 7 As shown, solid boxes represent polymer component 12 at pH 4, and hollow boxes represent polymer component 12 at pH 8. When treated at pH 4, most of the added polymer is fixed after curing at 120°C for 10 minutes, so increasing the curing time 18 or curing temperature 16 has almost no effect. The polymer content of L-PEMAc is much lower than that of H-PEMAc. The physical fixation effect of L-PEMAc is much worse.

[0054] Figure 8 The effect of curing temperature 16 on wet strength is shown. Solid boxes represent polymer composition 12 using pH 4, and hollow boxes represent polymer composition 12 using pH 8, where curing time 18 is 10 minutes, and the variable curing temperature 16 is shown on the X-axis. Wet strength increases with increasing curing temperature 16. The numbers next to the data points represent the corresponding constant yield.

[0055] Figure 9 The wet strength of cured pulp sheets treated at pH 4 is shown as a function of the corresponding fixed yield. Figure 9The scatter plots do not reflect noise or experimental error, but are caused by the use of a series of curing times (18), curing temperatures (16), PEMAc dosages, and PEMAc molecular weights. As mentioned above, circular data points are used for L-PEMAc, and square data points are used for H-PEMAc. The ideal result is no wet strength and a fixed yield of 1 ( Figure 9 (bottom right corner). Pulp flakes with a WTI below approximately 2 Nm / g are readily repulped in a standard laboratory shredder, while those reaching 3 Nm / g require more vigorous redispersion. For high molecular weight H-PEMAc, all but one exhibit high fixation yields. The main challenge with H-PEMA is maintaining a low WTI and thus preserving repulping capacity. In contrast, with L-PEMAc, WTI is lower, but many fixation yields are too low. Focusing on yields greater than 0.8 and WTIs < 3 Nm / g, we found that high yields and low wet strength can be obtained. However, Figure 9 The data description in the document does not mention the amount of polymer added, the curing temperature of 16°C, or the curing time of 18°C.

[0056] Figure 9 The experimental results revealed the existence of curing conditions that produce both high fixed yield and low WTI (i.e., good repulping properties). However, several adjustable parameters exist in our treatment study, including the polymer molecular weight, the amount of polymer applied to the untreated substrate 10, the pH of the polymer component 12 applied to the untreated substrate 10, the curing time 18, and the curing temperature 16. Unbound by theory, one potential reason for the increase in WTI during curing is the conversion of the carboxylic acid portion of the succinic acid to the corresponding succinic anhydride. In this paper, the degree to which the corresponding succinic acid portion forms anhydride is defined as the dimensionless parameter β, ranging from 1 to 0. β is the fraction of the succinic acid portion that has been converted to the succinic anhydride portion, a conversion that can occur during curing. It has been suggested that β is a good, simple measure of the progress of curing during heating of the treated pulp.

[0057] In the absence of precise measurements of the β value of the cured pulp sheets of this application, equations 1 and 2 below are used to estimate the β value corresponding to various curing conditions. The formation of succinic anhydride from succinic acid is a unimolecular first-order reaction. Therefore, β should depend on the curing time 18 and the curing temperature 16, but should be independent of the mass fraction of PEMAc (or other polymers) in the pulp sheet. Equation 1 gives a rate expression for the relationship between β and the curing time 18, i.e., t, where k r It is the rate constant for anhydride formation. The temperature dependence of the rate constant is given by the Arrhenius expression as shown in Equation 2. To apply Equation 1, the pulp temperature can be determined as a function of the curing time 18, therefore k in Equation 1... rIt can be expressed as a function of time. In the absence of detailed temperature / time data during curing, we assume isothermal curing and evaluate β using Equation 3. Two other assumptions used are that the reaction is irreversible and that the rate of water transport from the pulp is not rate-determining. These two assumptions are reasonable because, in experiments, β values ​​were low (mostly much less than 0.2) and the polymer deposits on the substrate surface were very thin.

[0058] Equation 1.

[0059] Equation 2.

[0060] Equation 3. β=1-exp(-k r t)

[0061] For PEMAc membranes dried from a pH 4 solution (without pulp), the activation energy E is... a =50 kJ / mol, and the pre-exponential factor A = 1.24 x 10⁻⁶. 3 s 1 The publicly available activation energy for PEMA is 56 kJ / mol, and for poly(vinyl methyl ether-alternating maleic anhydride) it is 78.7 kJ / mol. β is a useful parameter for describing the degree of curing because it encompasses both the curing time¹⁸ and the curing temperature¹⁶. However, in our experimental data, β is an estimate of the anhydride formation kinetics, not an actual measurement of the anhydride formation kinetics. The wet tensile index of the pulp sheet treated with PEMAc is expected to increase with the product of the applied polymer content, the fixed Γ (measured in meq / g), the applied Γ, and the degree of curing β.

[0062] Figure 10 This is a log / log plot showing the wet tensile index and the functional relationship between β and Γ for H-PEMAc-treated pulp in the experiment. The applied Γ(Γ) a The β value is determined based on the added polymer rather than the fixed polymer, and the β value is obtained by applying the experimental curing time 18 and curing temperature 16 to Equation 3 as shown above. The open box corresponds to experiments using very high doses of applied polymer, where Γ a >0.4 meg / g, or equivalently >25 kg of PEMA added per metric ton of dry pulp. The closed frame corresponds to Г. a Experiments with values ​​less than or equal to 0.4 meg / g. Based on... Figure 10 The dashed line fitted to the data points in the figure shows the power-law relationship between the wet tensile index and the product of βΓ. The empirical fitted line is calculated by Equation 4 below, where WTI represents the wet tensile index, b = 0.6, and a = 70 Nm / g. Figure 10The horizontal line in the figure indicates that WTI = 3 Nm / g. Most high-dose results (i.e., open boxes) fall below the power-law line. Figure 10 The power-law line in the figure fits the relationship between the wet stretching exponent and the product of βГ under the condition of a very high constant yield and Г < 0.4 meq / g. Figure 10 The βГ corresponding to the wet tensile index of 3 Nm / g was obtained. a3 =0.052 meq / g, corresponding to the intersection of the 3 Nm / g horizontal line and the power-law curve. This βΓ a3 The value can be used as a design tool to select curation conditions in larger-scale processing scenarios. The corresponding βГ a2 The value is 0.0027 meq / g, reflecting a more conservative design target, where βГ a2 βГ represents the wet tensile index corresponding to 2 Nm / g. a value.

[0063] Equation 4.

[0064] refer to Figure 11 , Figure 11 The wet tensile index and βΓ were compared under three conditions. a The relationships are as follows: strong pulp with high molecular weight polymers (dashed line near the Y-axis, bleached softwood pulp + H-PEMA), strong pulp with low molecular weight polymers (circles, bleached softwood pulp + L-PEMA), and fragile pulp with high molecular weight polymers (diamonds, bleached hardwood pulp + H-PEMA). All three combinations exhibit power-law behavior with a slope of 0.6. However, the weakest combination shifts to the right, giving a higher βΓ. a2 and βГ a3 Value. It is recommended to conduct laboratory handpaper studies for each new combination of polymer and substrate to generate a product with... Figure 10 and 11 The corresponding graph allows for the determination of βΓ for specific polymer and substrate combinations. a2 and / or βГ a3 Values. The table below summarizes them. Figure 11 These values.

[0065] Table 1

[0066] polymer pulp a(Nm / g) b <![CDATA[βГ2(meq / g)]]> <![CDATA[βГ3(meq / g)]]> H-PEMAc cork 70 0.6 0.0027 0.0052 L-PEMAc cork 45 0.6 0.0056 0.011 H-PEMAc hardwood 30 0.6 0.011 0.022

[0067] The power-law coefficients of Equation 4 and the corresponding re-pulping properties limit the... Figure 11 Extracting βГ from the drawn power-law line a3 The wet tensile index βГ was obtained as 2 Nm / g. a2 And βГ with wet tensile index = 3 Nm / g a3 .

[0068] While this disclosure has been described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that many other forms and modifications will be obvious. The methods and products described herein should generally be construed as covering all such apparent forms and modifications within the true scope of this disclosure.

Claims

1. A treated lignocellulose matrix comprising: A polymer immobilized to lignocellulose to form a treated matrix, wherein the polymer comprises a succinic acid moiety capable of reversibly varying between a succinic anhydride moiety and a succinic acid moiety, wherein the immobilized Γ(Γf) value represents the amount of polymer immobilized to the treated matrix, measured as milliequivalents of carboxyl groups titratable per gram of dry treated matrix polymer, wherein Γ f The value is at least 0.001 milliequivalents per gram of dried treated substrate, and said treated substrate has a wet tensile index of 3 Newton-meters per gram or less.

2. The treated lignocellulose substrate according to claim 1, wherein: The polymer comprises a copolymer of maleic anhydride, maleic acid, or a combination thereof with monomers selected from: acrylic acid, methacrylic acid, styrene sulfonic acid, vinyl sulfonic acid, acryloylaminomethylpropane sulfonic acid, diallyl dimethylammonium salt, acryloyl ethyl trimethylammonium salt, acryloyl ethyl dimethylamine, ethyl acryloyl ethyl trimethylammonium salt, ethyl acryloyl ethyl dimethylamine, methacryloyl ethyl trimethylammonium salt, methacryloyl ethyl dimethylamine, acryloylaminopropyl trimethylammonium salt, acryloylaminopropyl dimethylamine, methacryloylaminopropyl trimethylammonium salt, methacryloylaminopropyl dimethylamine, vinyl formamide, vinylamine, acrylamide, methacrylamide, N-alkylacrylamide, vinyl formamide, ethylene, methyl vinyl ether, octadecene, styrene, isobutylene, and mixtures thereof.

3. The treated lignocellulose substrate according to claim 1, wherein: The polymer is selected from poly(ethylene-co-maleic acid), poly(butadiene-co-maleic acid), and combinations thereof.

4. The treated lignocellulose substrate according to claim 1, wherein the polymer is a homopolymer formed from maleic acid or maleic anhydride.

5. The treated lignocellulose substrate according to any one of claims 1 to 4, wherein: The treated substrate comprises wood pulp.

6. The treated lignocellulose substrate according to any one of claims 1 to 4, wherein: The substrate comprises kraft pulp.

7. The treated lignocellulose matrix according to any one of claims 1 to 4, wherein the polymer has a weight-average molecular weight of 2 to 10,000 kilodaltons.

8. The treated lignocellulosic substrate according to any one of claims 1 to 4, wherein the wet tensile index of the treated substrate is 2 N·m / g or less.

9. A method for forming a treated lignocellulose substrate, the method comprising the following steps: A polymer component is applied to an untreated lignocellulosic matrix to form a polymer matrix assembly, wherein the polymer component comprises a polymer, and wherein the polymer comprises a succinic acid moiety capable of reversibly changing between a succinic anhydride moiety and a succinic acid moiety. The polymer is fixed to the untreated substrate by heating the polymer substrate assembly to a curing temperature of 100 degrees Celsius or higher and continuing to cure for a period of time to form a treated substrate; and When the wet tensile index of the treated substrate is 3 N·m / g or less, and when the fixed Γ(Γ) of the treated substrate is... f Heating of the polymer substrate assembly is terminated when the value reaches 0.001 milliequivalents or greater per gram of dried, treated substrate, wherein Γ f The value represents the amount of polymer fixed to the treated substrate, measured in milliequivalents of titratable carboxyl groups per gram of dry, treated substrate polymer; and When the product of βГ of the treated substrate (βГ) a The product of βГ and βГ corresponding to the wet tensile index of the treated substrate at 3 N·m / g is less than or equal to the product of βГ and βГ. a3 When ), heating of the treated substrate is terminated, where β(β) is the total succinic anhydride portion of the polymer divided by the total succinic acid portion of the polymer, and the applied Γ(Γ) of the treated substrate. a () is the amount of polymer added to the untreated substrate, expressed in milliequivalents per gram of dried treated substrate.

10. The method of claim 9, further comprising: The pH of the polymer substrate assembly was adjusted to between 2 and 5, and The process of fixing the polymer to an untreated substrate includes heating the polymer components and the untreated substrate to a curing temperature, wherein the curing temperature is 150 degrees Celsius or higher.

11. The method according to claim 9, wherein: Terminating heating includes producing the treated substrate, wherein the wet tensile index of the treated substrate is 2 N·m / g or less.

12. A method for forming a treated substrate, the method comprising the steps of: A polymeric component is applied to an untreated substrate to form a polymeric substrate assembly, wherein the untreated substrate comprises 25 to 100% by weight of lignocellulose based on the total weight of the dried untreated substrate, the polymeric component comprises a polymer, and wherein the polymer comprises a succinic acid moiety capable of reversibly varying between a succinic anhydride moiety and a succinic acid moiety, and wherein the polymer comprises a copolymer of maleic anhydride, maleic acid, or a combination thereof with monomers selected from: acrylic acid, methacrylic acid, styrene sulfonic acid, vinyl sulfonic acid, acryloylaminomethylpropane sulfonic acid, diallyl dimethyl... Ammonium salts, acryloylethyltrimethylammonium salts, acryloylethyldimethylamine, ethylacryloylethyltrimethylammonium salts, ethylacryloylethyldimethylamine, methacryloylethyltrimethylammonium salts, methacryloylethyldimethylamine, acryloylaminopropyltrimethylammonium salts, acryloylaminopropyldimethylamine, methacryloylaminopropyldimethylammonium salts, methacryloylaminopropyldimethylamine, vinylformamide, vinylamine, acrylamide, methacrylamide, N-alkylacrylamide, vinylformamide, ethylene, butadiene, methyl vinyl ether, octadecene, styrene, isobutylene, and mixtures thereof; Adjust the pH of the polymer substrate assembly to 2 to 5; The polymer is fixed to the untreated substrate to form the treated substrate by heating the polymer substrate assembly to a curing temperature of 120 to 500 degrees Celsius and continuing to cure for a period of time; and When the wet tensile index of the treated substrate is 3 N·m / g or less (TAPPI method T456 om-10 and / or T494 om-96), and when the fixed Γ(Γ) of the treated substrate is... f Heating of the polymer substrate assembly is terminated when the value reaches 0.001 milliequivalents or greater per gram of dried, treated substrate, wherein Γ f The value represents the amount of polymer fixed to the treated substrate, measured in milliequivalents of titratable carboxyl groups per gram of dried treated substrate polymer.

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