Digester additive formulations and use thereof for pulp production

Abstract

A digester additive formulation includes a combination of phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer. The digester additive formulation is as an additive for a kraft process for production of pulp from raw materials, such as wood chips. When used in the kraft pulping process, the digester additive formulation improves viscosity of the resulting pulp and increases pulp yield.

Description

DIGESTER ADDITIVE FORMULATIONS AND USE THEREOF FOR PULP PRODUCTIONBACKGROUND OF THE INVENTION

[0001] This application claims the benefit under 35 U.S.C. §119(e) of prior U.S. Provisional Patent Application No. 63 / 632,056 filed April 10, 2024, which is incorporated in its entirety by reference herein.

[0002] The present invention relates to a digester additive formulation for a pulping process, methods of using a digester additive formulation in the pulping process, and products thereof.

[0003] In the pulp making industry, kraft pulping is a common method of producing pulp from raw materials, such as wood chips. The production of pulp using the kraft pulping process involves cooking wood chips in a digester vessel (digester) at high temperatures and with the addition of sodium sulfide and caustic (cooking liquor). The cooking liquor is added to screened wood chips prior to the cooking. Once the wood chips and cooking liquor are added to the digester, the wood chip mixture is subjected to 200-370°F, and a pressure as high as 130 psi. The time it takes for digestion can vary between 4-8 hours. Digestion can occur either in a batch or a continuous process.

[0004] The result of the above-mentioned cooking process is the hydrolysis and / or depolymerization of the lignin of the wood chips. Whilst these conditions are somewhat directed at delignification, cellulose is also damaged during the cook. The Kappa number, also known as the Kappa value or K number, is a measure to quantify the lignin content in wood pulp. The lower the Kappa number, the more cellulose quality is impacted. During the cooking process, operators attempt to balance lignin removal and cellulose degradation. Thus, an objective of the process is to maximize pulp yield (as measured by the conversion of wood topulp), reduce rejects, and maintain the quality of the pulp (as measured with pulp viscosity and pulp strength).

[0005] Over many years, various additives have been used in an attempt to improve pulp production. These additives are broadly classified as catalysts and surfactants. Although the exact mechanism of catalysts is not fully elucidated, the catalysts appear to speed up the rate of delignification whilst also protecting the cellulose integrity. Anthraquinone (AQ) is the most commonly known of these catalysts and has been used since at least 1977. However, due to regulatory issues and toxicity concerns, this catalyst has fallen out of favor and is banned in many countries. There have been many research efforts to find better and safer AQ alternatives. None of these, however, have been commercialized.

[0006] In contrast to the catalysts, surfactants have a different mode of action. Specifically, surfactants do not increase the rate of delignification or protect the cellulose structure. Rather, surfactants function by reducing the surface activity of the cooking liquor, thereby ensuring wetting and thus better liquor penetration into the wood chips, which invariably results in more efficient cooking and less rejects. This typically results in better conversion of wood chips to pulp. Some examples of surfactants are shown in U.S. Patent No. 2,999,045 that describes the use of EO / PO block copolymers to improve pulp cooking in the digester whilst U.S. Patent No. 4,952,277 shows a process of making paper by adding to the medium surface-active molecules, such as ethoxylated nonylphenol alcohol.

[0007] Accordingly, a need exists for improving wood pulping processes in general and specifically, a need exists for improved digester additive formulations that facilitate a higher pulp viscosity and an increased pulp yield when used during a pulp making process.SUMMARY OF THE PRESENT INVENTION

[0008] A feature of the present invention is to provide a digester additive formulation for a kraft pulping process.

[0009] Another feature of the present invention is to provide a digester additive formulation that improves pulp viscosity and increases pulp yield from a kraft pulping process.

[0010] An additional feature of the present invention is to provide a wood pulp mixture for a kraft pulping process, which includes a digester additive formulation that improves pulp viscosity and increases pulp yield.

[0011] Another feature of the present invention to provide a method of making pulp by including a digester additive formulation that improves pulp viscosity and increases pulp yield of a kraft pulping process.

[0012] Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or can be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the formulations, elements, and combinations particularly pointed out in the description and appended claims.

[0013] To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention, in part, relates to a digester additive formulation for a kraft process for producing wood pulp. The digester additive formulation includes phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer. The phenyl tetracarboxylic acid is of the structure shown in Formula I:and the macromolecule polymer comprises a structure selected from the group of structures ofFormulae II- V:, the moiety[P,S] denotes either a phosphate group or a sulfate group, the moiety R can be either hydrogen, a hydrocarbyl group (e.g., containing from 1 to 16 carbon atoms), or an aryl group (e.g., containing from 1 to 16 carbon atoms), and each X can independently be hydrogen or a metal cation (e.g., K+ or Na+); andFormula V, wherein each ofRi and R2 can independently be hydrogen, a hydrocarbyl group (e.g., containing from 1 to 16 carbon atoms), or an aryl group (e.g., containing from 1 to 16 carbon atoms).

[0014] It has been found, according to the present invention, that a synergistic effect occurs from the combination of phenyl tetracarboxylic acid or a derivative or salt thereof, and one of a group of special macromolecule polymers, which forms the digester additive formulation of the present invention. Specifically, when adding the combination of phenyl tetracarboxylic acid or a derivative or salt thereof, and the macromolecule polymer, as a digester additive formulation during a kraft pulping process, pulp viscosity and pulp yield are significantly improved, as compared to a kraft pulping process without the use of the digester additive formulation.

[0015] The present invention further relates to a mixture comprising oven dried wood chips for use in a kraft process for making wood pulp, and the digester additive formulation of the present invention, wherein the digester additive formulation is present in the mixture in an amount of from 0.001% by weight to 10% by weight, based on the weight of the oven-dried wood chips, for example, in an amount of from 0.001% by weight to 8% by weight, in an amount of from 0.01% by weight to 8% by weight, in an amount of from 0.05% by weight to 7% by weight, in an amount of from 0.1 % by weight to 6% by weight, or in an amount of from 0.2% by weight to 2% by weight, based on the weight of the oven-dried wood chips.

[0016] The present invention further relates to a method comprising: mixing together wood chips, white liquor, dilution water, and the digester additive formulation of the present invention to form a wood pulp mixture.

[0017] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.BRIEF DESCRIPTION OF DRAWINGS

[0018] FIG. 1 is a bar graph showing the Kappa number after cooking, of the pulps made according to Example 2, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0019] FIG. 2 is a bar graph showing the percent (%) cook yield after cooking, of the pulps made in accordance with Example 2, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0020] FIG. 3 is a bar graph showing the percent (%) pulp viscosity, in centipoise (cPS), of the pulps made in accordance with Example 2, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0021] FIG. 4 is a bar graph showing the average Kappa number after cooking, of the pulps made according to Example 3, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, the pulp cooked with only the macromolecule polymer of Formula V as an additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0022] FIG. 5 is a bar graph showing the percent (%) cook yield after cooking, of the pulps made in accordance with Example 3, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, the pulp cooked with only the macromolecule polymer of Formula V as an additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0023] FIG. 6 is a bar graph showing the cooked pulp viscosity, of the pulps made in accordance with Example 3, and compares the pulp cooked as a negative control with no digester additive formulation, the pulp cooked with only the phenyl tetracarboxylic acid additive, the pulp cooked with only the macromolecule polymer of Formula V as an additive, and the pulp cooked with a synergistic digester additive formulation according to the present invention.

[0024] FIG. 7 is a bar graph showing the sugar analysis of treated and untreated pulps made in accordance with Example 3, wherein carbohydrate extraction and measurement was done according to the procedure TAPPI T204.DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0025] A digester additive formulation is provided for a kraft process of producing wood pulp. The digester additive formulation comprises a phenyl tetracarboxylic acid or a derivative or salt thereof in combination with a macromolecule polymer. When used as a digester additive formulation in a process of producing wood pulp, the phenyl tetracarboxylic acid or a derivative or salt thereof and the macromolecule polymer has a synergistic effect that improves the viscosity of the resulting pulp and the overall pulp yield.

[0026] As used herein, "pulp" also referred to herein as “wood pulp”, refers to a fibrous material derived from a raw wood material, such as wood chips, that has undergone a chemical, pressure, and temperature treatment, such as a kraft process.

[0027] “Kraft process,” also referred to herein as “kraft pulping” or “kraft pulping process,” is a process of chemically converting raw material, such as wood or wood chips, to pulp. The kraft process uses a “cooking liquor” as a chemical for “cooking” (chemical pulping process) the raw material, also referred to herein as “white liquor”, which can be a combination of sodium hydroxide and sodium sulfide, and optionally sodium carbonate and / or sodium polysulfide. The mixture of wood chips and white liquor are subjected to increased temperature and pressure in a digester vessel.

[0028] Unless stated otherwise, a “digester additive formulation” refers to a multicomponent additive that is added to a digester vessel (as separate components or pre-combined) during a pulp production process, such as a kraft process. A “digester additive formulation” does not consist of a single compound or molecule but rather refers to a multi-component additive.

[0029] “Macromolecule polymer” refers to a large molecule composed of repeating monomers that are covalently bonded together through polymerization reactions, forming long chains or networks.

[0030] “Block copolymer” refers to a type of polymer including two or more distinct polymer blocks, or segments, linked together covalently. These segments are typically composed of different monomers.

[0031] 'Surfactant" refers to an organic compound which can lower the surface tension of a liquid, the interfacial tension between two liquids, or the interfacial tension between a liquid and a solid.

[0032] According to various embodiments of the present invention, a digester additive formulation is provided for a kraft process for producing wood pulp. The digester additive formulation can include a phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer.

[0033] In certain embodiments, the phenyl tetracarboxylic acid has the structure shown in Formula I:Phenyl tetracarboxylic acid is also known in the art as 1 ,2,4,5 benzyl-tetracarboxylic acid. As an option, derivatives, salts, or a combination thereof, of the phenyl tetracarboxylic acid, can be used. For example, a derivate or salt of the phenyl tetracarboxylic acid can be used instead of Formula I in the digester additive formulation, or in addition to Formula I in the digester additive formulation.

[0034] The phenyl tetracarboxylic acid or derivative or salt thereof, can be a derivative of phenyl tetracarboxylic acid. The derivative of phenyl tetracarboxylic acid can be, for example, selected from the group consisting of alkyl-substituted phenyl monocarboxylic acids, alkylsubstituted phenyl dicarboxylic acids, alkyl-substituted phenyl tricarboxylic acids, and alkyl-substituted phenyl tetracarboxylic acids. The phenyl tetracarboxylic acid or derivative or salt thereof can be a salt of phenyl tetracarboxylic acid.

[0035] The phenyl tetracarboxylic acid or derivative or salt thereof, can be a substituted phenyl tetracarboxylic acid, that is, a structure including a substituted moiety on the phenyl ring. For example, the phenyl tetracarboxylic acid or derivative or salt thereof can be an alkylphenylsubstituted tetracarboxylic acid. The phenyl tetracarboxylic acid or derivative or salt thereof, can be an alkoxyphenyl-substituted tetracarboxylic acid. The phenyl tetracarboxylic acid or derivative or salt thereof, can be methoxylated, ethoxylated, propoxylated, or the like. The phenyl tetracarboxylic acid or derivative or salt thereof, can be a phenyl-substituted tetracarboxylic acid.

[0036] The phenyl tetracarboxylic acid or derivative or salt thereof is combined with a macromolecule polymer to form the digester additive formulation of the present invention. The macromolecule polymer is a large molecule composed of repeating structural units of monomers. The macromolecule polymer is characterized by a high molecular weight and long-chain structure.

[0037] The macromolecule polymer of the present invention can be a surfactant. A surfactant refers to an organic compound which can lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid.

[0038] The macromolecule polymer can comprise any of a number of specific structures. Certain macromolecule polymer structures have shown synergistic effects that improve the viscosity of resulting pulp and the overall pulp yield when used in combination with phenyl tetracarboxylic acid or a derivative or salt thereof, during a pulp production process.

[0039] The macromolecule polymer can be of the structure shown in Formula II:Formula II,wherein the value of each x in Formula II can independently be, for example, from 12 to 141 , and the value of y can be from 20 to 56. The value of the first x in Formula II can be the same or different than the value of the second x in Formula II. The sum of both x’s in Formula II can be, for example, from 24 to 282. The value of each x in Formula II can independently be from 15 to 75. The value of y in Formula II can be from 25 to 35. The macromolecule polymer structure of Formula II can be a block copolymer of polyethylene oxide and polypropylene oxide (an EO / PO block copolymer).

[0040] The macromolecule polymer can be of the structure shown in Formula III:Formula III, wherein the value of each x in Formula III can independently be from 12 to 141 and the value of y in Formula m can be from 20 to 56. The value of each x in Formula III can independently be from 15 to 75. The sums of the values of the two x’s in Formula III can be from 24 to 282. The value of the first x in Formula III can be the same or different than the value of the second x in Formula III. The value of y in Formula III can be from 25 to 35. The R group can be any alkyl, aryl, alkenyl, or alkynyl group, or the like. The R group can contain, for example, from 1 to 16 carbon atoms (e.g., from 1 to 12 carbon atoms or from 1 to 8 carbon atoms, or from 1 to 6 carbon atoms). The macromolecule polymer of Formula III can be, for example, a monoester of a fatty acid esterified from an EO / PO block copolymer.

[0041] Examples of fatty acids of Formula III can include, but are not limited to, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid (EP A), docosahexaenoic acid (DHA), elaidic acid, vaccenic acid, conjugated linoleic acid (CLA), ricinoleic acid, and eleostearic acid.

[0042] The macromolecule polymer can be of the structure shown in Formula IV :Formula IV, wherein the moiety [P,S] denotes either a phosphorus or a sulfur, but not both, the moiety R can be hydrogen, a hydrocarbyl group (e.g., containing from 1 to 16 carbon atoms or from 1 to 12 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms), or an aryl group (e.g., containing from 1 to 16 carbon atoms or from 1 to 12 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms), and each X can independently be hydrogen or a metal cation (e.g., K+ or Na+). In Formula IV, both X’s can be same or different. In Formula IV, each X can be hydrogen. In Formula IV, the value of x can be from 5 to 100, for example, from 6 to 20, and the value of y can be from 8 to 40, for example, from 10 to 20. The macromolecule polymer of Formula IV can be, for example, a linear alkyl ethoxylated phosphate or a linear alkyl ethoxylated sulfate.

[0043] The macromolecule polymer can be of the structure shown in Formula V:Formula V, wherein each of Ri andR2 can independently be hydrogen, a hydrocarbyl group (e.g., containing from 1 to 16 carbon atoms or from 1 to 12 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms), or an aryl group (e.g., containing from 1 to 16 carbon atoms or from 1 to 12 carbon atoms or from 1 to 8 carbon atoms or from 1 to 6 carbon atoms), the value of x can be from 3 to 50, for example, from 3 to 10, and the value of y can be from 2 to 40, for example, from 2.5 to 30. In Formula V, each of Ri and R2 can be hydrogen. The macromolecule polymer of Formula V can be, for example, a linear alkyl ethoxylated alcohol (an LEA), for example, wherein when Ri is hydrogen,Ri is a secondary alcohol, or Ri is an alkyl substituent. In Formula V, Ri can be a secondary alcohol, alkyl substituent. The macromolecule of Formula V can be used with, for example, an alcohol initiator that is a branched primary alcohol. The macromolecule of Formula V can be used with, for example, an alcohol initiator that is a branched primary alcohol comprising branching substituents that are alkyl groups and are attached to any position of the primary alcohol.

[0044] The digester additive formulation can be a combination of phenyl tetracarboxylic acid or derivative or salt thereof and Formula II, phenyl tetracarboxylic acid or derivative or salt thereof and Formula III, phenyl tetracarboxylic acid or derivative or salt thereof and Formula IV, phenyl tetracarboxylic acid or derivative or salt thereof and Formula V, or phenyl tetracarboxylic acid or derivative or salt thereof and any combination of Formula II, Formula III, Formula IV, and Formula V.

[0045] The weight ratio of the phenyl tetracarboxylic acid or derivative or salt thereof, also referred to as the PTA, to the macromolecule polymer(s), can be a ratio that effects a synergistic effect. The weight ratio of the PTA to the macromolecule polymer(s) can be, for example, from 1 :100 to 100: 1. For example, the weight ratio of the PTA to the macromolecule polymer(s) can be from 1:50 to 5: 1, from 1:10 to 1:1, from 1:5 to 5:1. The weight ratio of the PTA to the macromolecule polymer(s) can be, for example, from 0.1 : 10 to 10: 1 , from 0.5: 1 to 1.5: 1 , or about 0.5:1.5.

[0046] The present invention further includes a method of using a digester additive formulation in a kraft pulping process. The kraft process is a method for converting wood into pulp for papermaking. The process can begin with the preparation of wood chips. Various species of wood can be used, including hardwoods and / or softwoods. The wood can be debarked and chipped into small pieces, which increases the surface area for subsequent processing. The wood chips can then be dried using an oven or the like. The wood chips are then subjected to a chemical pulping process known as “cooking.” In the kraft process, the cooking liquor consists of a mixtureof sodium hydroxide (NaOH) and sodium sulfide (Na2S), and, optionally, sodium carbonate (NazCOd and / or sodium polysulfide (Na2Sx). This mixture is also referred to as white liquor. The wood chips are cooked in a digester vessel (digester) under high temperature and pressure conditions. During cooking, the lignin in the wood is dissolved by the alkaline solution, while the cellulose fibers remain largely intact.

[0047] The concentration of sodium hydroxide in white liquor can vary depending on factors such as pulp yield, pulp quality requirements, and process conditions. Higher concentrations of sodium hydroxide may be used for more efficient delignification and pulp bleaching. The ratio of sodium hydroxide to sodium sulfide can be adjusted to control the degree of sulfidity in the pulping process, which affects pulp yield, pulp strength, and bleachability. Sodium carbonate can be added to white liquor to increase the carbonate content, which can help buffer the alkalinity of the solution and stabilize pH during pulping.

[0048] In addition to the digestive additive of the present invention, other additives can be used during the cooking process as long as they do not interfere with the indicated function of the digester additive formulation. For example, antiscalants, dispersants, chelating agents, and foaming agents can be used.

[0049] Examples of antiscalants and dispersants can include, but are not limited to, phosphonates, polyacrylate, polyphosphates, organic polymers, other surfactants, and the like. Antiscalants and dispersants can help prevent scaling and deposition of inorganic compounds on equipment surfaces, such as black liquor evaporators and recovery boilers.

[0050] Examples of chelating agents can include, but are not limited to, Ethylenediaminetetraacetic acid, Diethylenetriaminepentaacetic acid, Nitrilotriacetic acid, and N- (2-Hydroxyethyl)ethylenediaminetriacetic acid, and the like. Other chelants that can be used include Hydroxyethylethylenediaminetriacetic (HEDTA) and Diethylenetriamine pentaaceticacid (DPT A). Chelating agents can be added to sequester metal ions that could interfere with the pulping process or cause quality issues in the final paper product.

[0051] Examples of foaming agents can include, but are not limited to, silicone-based antifoams, mineral-oil based antifoams, fatty alcohol-based antifoams, polymer-based antifoams, and the like. Foaming agents can be used to control foam formation in various stages of the pulping process, such as in the digester or brown stock washer.

[0052] The cooking process dissolves and removes lignin from the wood chips. Lignin is a complex polymer that binds the cellulose fibers together in the wood. By breaking down the lignin, the cellulose fibers are separated, allowing them to be converted into pulp. After cooking, the pulp is washed to remove the spent cooking liquor, as well as other dissolved and suspended materials, such as residual lignin, extractives, and degradation products. This washing step is for removing impurities and ensuring the quality of the pulp.

[0053] Depending on the desired properties of the final paper product, the pulp can undergo a bleaching process to further remove color and residual lignin. Bleaching agents such as chlorine dioxide, hydrogen peroxide, ozone, and the like can be used to achieve the desired brightness and purity of the pulp. Once the pulp has been cooked, washed, and optionally bleached, it is ready for further processing or storage. The pulp can be further refined, blended with other pulps, or formed into sheets for papermaking.

[0054] For purposes of the present invention, the digestive additive formulation means a preformed formulation, and / or one that forms in-situ by separate addition of each component, and / or is the presence of a) the phenyl tetracarboxylic acid or derivative or salt thereof and b) the macromolecule polymer(s) amongst either the wood chips, and / or the white and / or black liquor, and / or the dilution medium or water.

[0055] The digester additive formulation of the present invention is added to the digester prior to or during the cooking process. In certain embodiments, the digester additive formulation canbe combined with the cooking liquor and then added to the digester. In other embodiments, the digester additive formulation and the cooking liquor can be added to the digester separately. In other embodiments, dried wood chips, cooking liquor, and the digester additive formulation can be combined together prior to cooking and then added to the digester.

[0056] The digester additive formulation can be added to the digester as a combined formulation, including the phenyl tetracarboxylic acid or derivative or salt thereof and the macromolecule polymer(s). Alternatively, the phenyl tetracarboxylic acid or derivative or salt thereof and the macromolecule polymer(s) can be added to the digester separately, and in any order. The digester additive formulation and the cooking liquor can be added to the digester as a batch or in a continuous manner during the cooking process.

[0057] In the present invention, the phenyl tetracarboxylic acid or a derivative or salt thereof can be added prior to, at the same time as, or after the adding of the macromolecule polymer. For instance, the phenyl tetracarboxylic acid or a derivative or salt thereof can be added within 1 second, within 5 seconds, within 15 seconds, within 1 minute, within 5 minutes, or within 10 minutes (or other times) of the adding of the macromolecule polymer. The phenyl tetracarboxylic acid or a derivative or salt thereof can be added as a mixture with the macromolecule polymer. The phenyl tetracarboxylic acid or a derivative or salt thereof can be added separately (e.g., by way of separate feed lines) with the macromolecule polymer. The phenyl tetracarboxylic acid or a derivative or salt thereof can be added as a single dose, as multiple doses, or on a continuously or semi-continuous feed to the source water. The macromolecule polymer can be added as a single dose, as multiple doses, or on a continuously or semi-continuous feed to the source water.

[0058] An amount of digester additive formulation that is added for a single cooking process, also referred to as the dosage, can be from 0.001% by weight or more, such as from 0.001% by weight to 10% by weight, from 0.01% by weight to 9% by weight, from 0.1% by weight, to 8% by weight, from 0.2% by weight to 7% by weight, from 0.3% by weight to 6% by weight, from0.4% by weight to 5% by weight, from 0.5% by weight to 4% by weight, from 0.6% by weight to 3% by weight, from 0.7% by weight to 2% by weight, from 0.8% by weight to 1.5% by weight, or from 0.9% by weight to 1.4% by weight, based on the weight of oven-dried wood chips that are cooked during the single cooking process, or in another range based upon any two of the values described above. TAPPI UM 23 is a method for determining the weight of wood chips on a moisture-free basis per unit volume and can be used to determine the weight of wood chips, on a moisture-free basis, per unit volume.

[0059] The present invention also provides a mixture of oven dried wood chips for use in a kraft process for making wood pulp, and a digester additive formulation as described herein. The digester additive formulation can be present in the mixture in an amount of 0.001% by weight or more, such as from 0.001% by weight to 10% by weight, based on the weight of the oven-dried wood chips, for example, in an amount of from 0.01 % by weight to 8% by weight, or in an amount of from 0.05% by weight to 7% by weight, or in an amount of from 0.1% by weight to 6% by weight, or in an amount of from 0.2% by weight to 2% by weight, based on the weight of the oven-dried wood chips.

[0060] The digester additive formulation can be mixed with wet wood chips and can be added in amounts based on what the wood chips would weigh if oven-dried or based on a measured oven-dried weight of the wood chips.

[0061] The present invention also provides a wood pulp mixture for use in a kraft process for making wood pulp. The wood pulp mixture can comprise wood chips, white liquor, dilution water, and a digester additive formulation as described herein. The digester additive formulation can be present in the mixture in an amount of 0.001% by weight or more, such as from 0.001% by weight to 10% by weight, based on the weight of the oven-dried wood chips, for example, in an amount of from 0.01% by weight to 8% by weight, in an amount of from 0.05% by weight to7% by weight, in an amount of from 0.1% by weight to 6% by weight, or in an amount of from0.2% by weight to 2% by weight, based on the weight of the oven-dried wood chips.

[0062] The digester additive formulation can be mixed with wet wood chips and can be added in amounts based on what the wood chips would weigh if oven-dried or based on a measured oven-dried weight of the wood chips.

[0063] The present invention also provides a method that comprises mixing together wood chips, white liquor, dilution water, and a digester additive formulation as described herein, to form a wood pulp mixture. The phenyl tetracarboxylic acid or derivative or salt thereof, and a macromolecule polymer, can first be mixed together to form the digester additive formulation, before the digester additive formulation is mixed with one or more of the wood chips, the white liquor, and the dilution water.

[0064] The method can involve first mixing together the wood chips, the white liquor, and the dilution water, to form a precursor mixture, and then separately adding the phenyl tetracarboxylic acid or derivative or salt thereof, and the macromolecule polymer, to form the wood pulp mixture. As such, the digester additive formulation can be formed in-situ, in the precursor mixture.

[0065] The method can involve forming a wood pulp from the wood pulp mixture, and forming a paper from the wood pulp, for example, carrying out an entire kraft process. The method and digester additive formulation improve pulp viscosity of the resulting wood pulp, improve the yield of the wood pulp, and reduce rejects when forming the wood pulp, when compared with the same method but carried out without the use of the digester additive formulation.

[0066] Once the wood chips and cooking liquor are added to the digester, the wood chip mixture is subjected to temperatures of from 180°F to 420°F, from 200°F to 370°F, from 220°F to 360°F, from 250°F to 350°F, from 260°F to 340°F, from 270°F to 330°F, from 280°F to 320°F, from 290°F to 310°F, from 295°F to 300°F, or in another range based upon any two of the valuesdescribed above. The wood chip mixture is further subjected to a pressure of from 80 psi to 160 psi, from 85 psi to 155 psi, from 90 psi to 150 psi, from 95 psi to 145 psi, from 100 psi to 140 psi, from 105 psi to 135 psi, from 110 psi to 130 psi, from 115 psi to 125 psi, from 118 psi to 120 psi, or in another range based upon any two of the values described above. The time for digestion can be from 3 hours to 10 hours, from 3.5 hours to 9.5 hours, from 4 hours to 9 hours, from 4.5 hours to 8.5 hours, from 5 hours to 8 hours, from 5.5 hours to 7.5 hours, from 6 hours to 7 hours, or in another range based upon any two of the values described above. After the time frame has elapsed, a wood pulp is rendered as a result of the cooking process.

[0067] The wood pulp resulting from the kraft pulping process using the digester additive formulation of the present invention can have a viscosity of from 55 cPS to 70 cPS, from 56 cPS to 69 cPS, from 57 cPS to 68 cPS, from 58 cPS to 67 cPS, from 59 cPS to 66 cPS, from 60 cPS to 65 cPS, from 61 cPS to 64 cPS, from 62 cPS to 63 cPS, at 25 °C and 1 atmosphere of pressure, or in another range based upon any two of the values described above.

[0068] Higher viscosity pulp typically contains longer and more entangled fibers, which can contribute to increased paper strength. This is particularly useful for applications where the paper withstands higher mechanical stress, such as packaging materials, cardboard, or paper bags. Higher viscosity pulp can improve the formation of paper sheets, leading to smoother and more uniform surfaces. Higher viscosity pulp tends to have slower drainage rates, allowing for better control over water removal during the papermaking process. In some cases, higher viscosity pulp may require fewer chemical additives such as retention aids or sizing agents to achieve desired paper properties, which results in cost savings and environmental benefits by reducing chemical usage and waste. Higher viscosity pulp can improve the runnability of paper machines by reducing the risk of web breaks and improving machine stability.

[0069] The percentage yield of pulp resulting from the kraft pulping process using the digester additive formulation of the present invention can be from 53.5% by weight to 60% byweight, from 54% by weight to 59.5% by weight, from 54.5% by weight to 59% by weight, from55% by weight to 58.5% by weight, from 55.5% by weight to 58% by weight, from 56% by weight to 57.5% by weight, from 56.5% by weight to 57% by weight, based on the ratio of the weight the pulp to the weight of the oven-dried wood chips, or in another range based upon any two of the values described above.

[0070] The “Kappa number” refers to a measure of the lignin content in wood pulp. The Kappa number can be determined by titrating a pulp sample with a standardized solution of potassium permanganate under acidic conditions. The Kappa number quantifies the lignin content based on the volume of permanganate consumed during the titration. A higher Kappa number indicates a higher lignin content in the pulp. The wood pulp resulting from the kraft pulping process using the digester additive formulation of the present invention can have a Kappa number of from 16.6 to 18, from 16.7 to 17.9, from 16.8 to 17.8, from 16.9 to 17.7, from 17 to 17.6, from 17.1 to 17.5, from 17.2 to 17.4, 17.25 to 17.3 or in another range based upon any two of the values described above.

[0071] Wood chips suitable for use in the production of pulp in the present invention can be derived from hardwood tree species, softwood tree species, or combinations thereof. Softwood tree species include, but not limited to: fir (such as Douglas fir and balsam fir), pine (such as Eastern white pine and Loblolly pine), spruce (such as white spruce), larch (such as Eastern larch), cedar, and hemlock (such as Eastern and Western hemlock). Examples of hardwood tree species include, but are not limited to: acacia, alder (such as red alder and European black alder), aspen (such as quaking aspen), beech, birch, oak (such as white oak), gum trees (such as eucalyptus and sweet gum), poplar (such as balsam poplar, Eastern cottonwood, black cottonwood, and yellow poplar), maple (such as sugar maple, red maple, silver maple, and big leaf maple). These types of woods can be used individually or in any combinations thereof. As an option, a combination of hemlock and cottonwood particulates can be used. As an option, the wood chips to be pulpedinclude virgin wood material, such as at least 50% by weight up to 100% by weight virgin wood material.

[0072] In addition to the digester additive formulation, the pulp may be treated with one or more optional additives as long as they do not interfere with the indicated function of the digester additive formulation. A list of optional chemical additives that can be used in conjunction with the present invention include, for example, pH modifiers, dry strength agents, wet strength agents, softening agents, debonding agents, adsorbency agents, sizing agents, dyes, optical brighteners, chemical tracers, opacifiers, dryer adhesive chemicals, and the like. Additional optional chemical additives may include, for example, pigments, emollients, humectants, viricides, bactericides, buffers, waxes, fluoropolymers, odor control materials and deodorants, zeolites, perfumes, vegetable and mineral oils, polysiloxane compounds, other surfactants, moisturizers, UV blockers, antibiotic agents, lotions, fungicides, preservatives, aloe-vera extract, vitamin E, or the like. Suitable optional chemical additives can be retained by the pulp fibers and may or may not be water soluble or water dispersible.

[0073] The present invention will be further clarified by the following examples, which are intended to be only exemplary of the present invention. Unless indicated otherwise, all amounts, percentages, ratios and the like used herein are by weight.EXAMPLESExample 1

[0074] Example 1 provides a hypothetical exemplary kraft process of pulp cooking using the digester additive formulation of the present invention. In the process of pulp cooking, a known mass of Eucalyptus wood chips is weighed and added to a reactor vessel. Specifically, 100 kg of wood chips was added, 0.2 kg of PTA was added, and 0.4 kg of macromolecules was added. Then, a measured amount of white liquor, dilution water, and a digester additive formulation are mixedwith each other and added to the reactor vessel. The ratio of white liquor added, to wood chips, was 3.5:1.

[0075] The reactor vessel is then heated from an initial temperature of 98°C to a final temperature of 155°C. The reactor vessel is then agitated. While the reactor vessel is agitated, the temperature is automatically adjusted to follow the required temperature profile. An H-factor is used as a measure of the combined effects of time and temperature during the cooking process. The H-factor is calculated using the following formula:H= t x e<T-loom75where: H is the H-factor, t is the cooking time in hours, e is a constant, and T is the cooking temperature in degrees Celsius. Once the predetermined H-Factor is reached, the reactor vessel temperature is allowed to cool down. An exemplary range of suitable H-factors can be from 300 to 475.

[0076] After cooling, the liquor is filtered and the resulting pulp is diluted, mixed, and washed. Finally, the pulp is screened through a 0.010” screen and the rejects are screened out. Rejects refers to the residual material or by-products that are separated from the pulp. A TAPPI T204 procedure can be followed for DCM extractives analysis.Example 2

[0077] Experiments were conducted to compare pulps that resulted from a kraft process without any additives, a kraft process using only phenyl tetracarboxylic acid as a digester additive formulation, and a kraft process using an embodiment of the present invention as a digester additive formulation.

[0078] The pulp cooking process of Example 1 was used to yield three different pulps. Specifically, a control pulp was yielded using the process of Example 1 without the use of any digester additive formulations. A PTA pulp was yielded using the process of Example 1 using only phenyl tetracarboxylic acid (PTA) (Formula 1) as a digester additive formulation. A PTA-LEA pulp was yielded using the process of Example 1 using PTA and linear alkyl ethoxylated alcohol (LEA) surfactant (Formula V) as the digester additive formulation. Each of the three pulps were tested to determine a Kappa number, a percentage cook yield, and a pulp viscosity.

[0079] As shown in the bar graph of FIG. 3, the synergistic combination of the PTA and LEA significantly improved the pulp viscosity for the PTA-LEA pulp as compared to the control pulp and the PTA pulp. The viscosity provided in FIG. 3 is measured at 25 °C and 1 atmosphere of pressure. The bar graph of FIG. 2 further shows a significant improvement in percentage of cook yield of the PTA-LEA pulp as compared to the control pulp and the PTA pulp. The percentage provided in FIG. 2 was determined based on a ratio of the total weight of the pulp to the total weight of the oven-dried wood chips. FIG. 1 further shows that the Kappa number of the PTA- LEA pulp was higher than the control pulp and the PTA pulp. The significant improvement in pulp yield and viscosity of the PTA-LEA pulp was attributed to the synergistic combination of the phenyl tetracarboxylic acid of Formula I and the linear alkyl ethoxylated alcohol surfactant of Formula V when used as the digester additive formulation in the kraft pulp cooking process.Example 3

[0080] Experiments were conducted to compare pulps that resulted from a kraft process without any digester additive formulations, a kraft process using only phenyl tetracarboxylic acid as a digester additive formulation, a kraft process using only a surfactant as a digester additive formulation, and a kraft process using an embodiment of the present invention as a digester additive formulation.

[0081] The pulp cooking process of Example 1 was used to yield four different pulps to further demonstrate the synergistic effect of the combination of the phenyl tetracarboxylic acid of Formula I and the linear alkyl ethoxylated alcohol surfactant of Formula V of the present invention. Specifically, a control pulp was yielded using the process of Example 1 without the use of any digester additive formulations. A PTA pulp was yielded using the process of Example11 and only phenyl tetracarboxylic acid (PT A) as the digester additive formulation. A LEA pulp was yielded using the process of Example 1 using only linear alkyl ethoxylated alcohol (LEA) surfactant as the digester additive formulation. A PTA-LEA pulp was yielded using the process of Example 1 using PTA and LEA surfactant as a digester additive formulation. Each of the four pulps were tested to determine a Kappa number, a percentage cook yield, and a pulp viscosity.

[0082] As shown in the bar graph of FIG. 6, the synergistic combination of the PTA and LEA significantly improved the pulp viscosity for the PTA-LEA pulp as compared to the control pulp, the LEA pulp, and the PTA pulp. The viscosity provided in FIG. 6 was measured at 25 °C and 1 atmosphere of pressure. As can be seen in FIG. 6, the amount of PTA used on the wood chips was 0.4% by weight. The amount of LEA used on the wood chips was also 0.4% by weight and the amount of the combination of PTA and LEA, used on the wood chips, was also 0.4% by weight. The bar graph of FIG. 5 further shows a significant improvement in percentage of cook yield of the PTA-LEA pulp as compared to the control pulp, the LEA pulp, and the PTA pulp. The percentages provided in FIG. 5 were determined based on a ratio of the total weight of the pulp to the total weight of the oven-dried wood chips. FIG. 4 further shows that the Kappa number of the PTA-LEA pulp was higher than the control pulp, the LEA pulp, and the PTA pulp. As is demonstrated by FIGS. 4-6, the PTA used as an additive on its own and the LEA used as an additive on its own were significantly less effective as compared to the combination of PTA and LEA. The significant improvement in pulp yield and viscosity of the PTA-LEA pulp was attributed to the synergistic combination of the phenyl tetracarboxylic acid of Formula 1 and the linear alkyl ethoxylated alcohol surfactant of Formula V, when together used as the digester additive formulation in the kraft process.Example 4

[0083] An extractive analysis was performed on the control pulp, the LEA pulp, the PTA pulp, and the PTA-LEA pulp of Example 3. Specifically, TAPPI T204 standard was followed forDCM extractives analysis. TAPPI T204 is a testing standard established by the Technical Association of the Pulp and Paper Industry (TAPPI). TAPPI T204 provides a method for testing the solubility of wood pulp. This test evaluates the quality and characteristics of pulp, particularly in the papermaking process. The method outlined in TAPPI T204 standard was adapted for the extraction and analysis of organic compounds of the pulp using dichloromethane (DCM) as the solvent. Using TAPPI T204 standard, carbohydrates were extracted and measured, and the results are shown in FIG. 7.

[0084] As demonstrated in the bar graph of FIG. 7, the percentage of carbohydrate extract by weight is similar when comparing the control pulp, the LEA pulp, the PTA pulp, and the PTA- LEA pulp.

[0085] Hemicellulose directly impacts the viscosity of pulp and the higher the hemicellulose content, the higher the pulp viscosity. Based on the carbohydrate analysis, it is clear that the increased viscosity of the PTA-LEA pulp shown in FIG. 6 is not due to an increase in hemicellulose content, which demonstrates that including the combination of the phenyl tetracarboxylic acid of Formula I and the linear alkyl ethoxylated alcohol surfactant of Formula V, as a digester additive formulation in the kraft process, impacts the overall cellulose structure.

[0086] The present invention includes the following aspects / embodiments / features in any order and / or in any combination:1. The present invention relates, in part, to a digester additive formulation for a kraft process for producing wood pulp, the digester additive formulation comprising phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, wherein the phenyl tetracarboxylic acid is of the structure shown in Formula I:Formula I and the macromolecule polymer comprises a structure selected from the group of structures ofFormulae II- V:[P,S] denotes either a phosphorus or a sulfur, but not both, the moiety R can be hydrogen, a hydrocarbyl group, or an aryl group, and each X can independently be hydrogen or a metal cation(e.g., selected from K+ and Na+); andFormula V, wherein each of Ri and R2 can independently be hydrogen, a hydrocarbyl group (e.g., containing from 1 to 16 carbon atoms), or an aryl group (e.g., containing from 1 to 16 carbon atoms).2. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure ofFormula II and is a block copolymer of polyethylene oxide and polypropylene oxide (an EO / PO block copolymer).3. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of each x in Formula II is independently from 5 to 110, the value of y in Formula II is from 10 to 40, and the sum of the values of both x’s is from 10 to 115.4. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of each x in Formula II is independently from 10 to 20, and the value of y in Formula II is from 25 to 35.5. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula III.6. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula III and R contains from 1 to 16 carbon atoms.7. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula III and is a monoester of a fatty acid esterified from an EO / PO block copolymer.8. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of each x in Formula III is independently from 5 to 110 and the value of y in Formula III is from 10 to 40.9. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of each x in Formula III is independently from 10 to 20 and the value of y in Formula III is from 25 to 35.10. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula IV.11. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises a linear alkyl ethoxylated phosphate or a linear alkyl ethoxylated sulfate.12. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula IV, and each X is hydrogen.13. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula IV and R is hydrogen.14. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of x in Formula IV is from 5 to 110 and the value of y in Formula IV is from 10 to 40.15. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of x in Formula IV is from 10 to 20 and the value of y in Formula IV is from 25 to 35.16. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises the structure of Formula V.17. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the macromolecule polymer comprises a linear alkyl ethoxylated alcohol.18. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein each of Ri and R2 is hydrogen.19. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein Ri is different than R2.20. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein Ri and R2 are the same.21. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of in Formula V is from 5 to 110 and the value of y in Formula V is from 10 to 40.22. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the value of x in Formula V is from 10 to 20 and the value of y in Formula V is from 25 to 35.23. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, is a derivative of phenyl tetracarboxylic acid.24. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the derivative of phenyl tetracarboxylic carboxylic acid is selected from the group consisting of alkyl-substituted phenyl monocarboxylic acids, alkylsubstituted phenyl dicarboxylic acids, alkyl-substituted phenyl tricarboxylic acids, and alkylsubstituted phenyl tetracarboxylic acids.25. The digester additive formulation of any preceding or following embodiment / feature / aspect, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, is a salt of phenyl tetracarboxylic acid.26. The present invention further relates to a mixture comprising oven dried wood chips for use in a kraft process for making wood pulp, and the digester additive formulation of anypreceding or following embodiment / feature / aspect, wherein the digester additive formulation is present in the mixture in an amount of from 0.001% by weight to 8% by weight, based on the weight of the oven-dried wood chips.27. The present invention further relates to a wood pulp mixture for use in a kraft process for making wood pulp, the mixture comprising wood chips, white liquor, dilution water, and the digester additive formulation of any preceding or following embodiment / feature / aspect.28. The wood pulp mixture of any preceding or following embodiment / feature / aspect, wherein the digester additive formulation is present in the mixture in an amount of from 0.001% by weight to 8% by weight, based on a dry weight of the wood chips.29. The present invention further relates to a method comprising: mixing together wood chips, white liquor, dilution water, and the digester additive formulation of any preceding or following embodiment / feature / aspect, to form a wood pulp mixture.30. The method of any preceding or following embodiment / feature / aspect, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, are first mixed together to form the digester additive formulation, before the digester additive formulation is mixed with the wood chips, the white liquor, and the dilution water.31. The method of any preceding or following embodiment / feature / aspect, further comprising first mixing together the wood chips, the white liquor, and the dilution water, to form a precursor mixture, and then adding separately the phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, so that the digester additive formulation is formed in-situ, in the precursor mixture, to form the wood pulp mixture.32. The method of any preceding or following embodiment / feature / aspect, further comprising forming a wood pulp from the wood pulp mixture, and forming a paper from the wood pulp, according to a kraft process.33. The method of any preceding or following embodiment / feature / aspect, wherein the method improves pulp viscosity of the wood pulp, improves yield of the wood pulp, and reduces rejects in forming the wood pulp, when compared with the same method but carried out without the use of the digester additive formulation.

[0087] The present invention can include any combination of these various features or embodiments above and / or below as set forth in sentences and / or paragraphs. Any combination of disclosed features herein is considered part of the present invention and no limitation is intended with respect to combinable features.

[0088] Applicants specifically incorporate the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

[0089] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present invention without departing from the spirit or scope of the present invention. Thus, it is intended that the present invention covers other modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A digester additive formulation for a kraft process for producing wood pulp, the digester additive formulation comprising phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, wherein the phenyl tetracarboxylic acid is of the structure shown in Formula I:Formula I and the macromolecule polymer comprises a structure selected from the group of structures of Formulae II-V:, wherein R is selected from an alkyl group, an aryl group, an alkenyl group, or an alkynyl group;Formula IV, wherein the moiety[P,S] denotes either a phosphorus or a sulfur, but not both, the moiety R is selected from hydrogen, a hydrocarbyl group, or an aryl group, and each X is independently hydrogen or a metal cation; andFormula V, wherein each of Ri and R2 is independently hydrogen, a hydrocarbyl group, or an aryl group.

2. The digester additive formulation of claim 1, wherein the macromolecule polymer comprises the structure of Formula II and is a block copolymer of polyethylene oxide and polypropylene oxide (an EO / PO block copolymer).

3. The digester additive formulation of claim 2, wherein the value of each x in Formula II is independently from 5 to 110, the value of y in Formula II is from 10 to 40, and the sum of the values of both x’s is from 10 to 115.

4. The digester additive formulation of claim 2, wherein the value of each x in Formula II is independently from 10 to 20, and the value of y in Formula II is from 25 to 35.

5. The digester additive formulation of claim 1, wherein the macromolecule polymer comprises the structure of Formula III.

6. The digester additive formulation of claim 5, wherein R contains from 1 to 16 carbon atoms.

7. The digester additive formulation of claim 5, wherein the macromolecule comprises a monoester of a fatty acid esterified from an EO / PO block copolymer.

8. The digester additive formulation of claim 7, wherein the value of each x in Formula III is independently from 5 to 110 and the value of y in Formula III is from 10 to 40.

9. The digester additive formulation of claim 7, wherein the value of each x in Formula III is independently from 10 to 20 and the value of y in Formula III is from 25 to 35.

10. The digester additive formulation of claim 1, wherein the macromolecule polymer comprises the structure of Formula IV.

11. The digester additive formulation of claim 10, wherein the macromolecule polymer comprises a linear alkyl ethoxylated phosphate or a linear alkyl ethoxylated sulfate.

12. The digester additive formulation of claim 10, wherein each X is hydrogen.

13. The digester additive formulation of claim 10, wherein R is hydrogen.

14. The digester additive formulation of claim 10, wherein the value of x in Formula IV is from 5 to 110 and the value of y in Formula IV is from 10 to 40.

15. The digester additive formulation of claim 10, wherein the value of x in Formula IV is from 10 to 20 and the value of y in Formula IV is from 25 to 35.

16. The digester additive formulation of claim 1, wherein the macromolecule polymer comprises the structure of Formula V17. The digester additive formulation of claim 16, wherein the macromolecule polymer comprises a linear alkyl ethoxylated alcohol.

18. The digester additive formulation of claim 16, wherein each of Ri and R2 is hydrogen.

19. The digester additive formulation of claim 16, wherein Ri is different than R2.

20. The digester additive formulation of claim 16, wherein Ri and R2 are the same.

21. The digester additive formulation of claim 16, wherein the value of x in Formula V is from5 to 110 and the value of y in Formula V is from 10 to 40.

22. The digester additive formulation of claim 16, wherein the value of x in Formula V is from 10 to 20 and the value of y in Formula V is from 25 to 35.

23. The digester additive formulation of claim 1, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, is a derivative of phenyl tetracarboxylic acid.

24. The digester additive formulation of claim 23, wherein the derivative of phenyl tetracarboxylic carboxylic acid is selected from the group consisting of alkyl-substituted phenyl monocarboxylic acids, alkyl-substituted phenyl dicarboxylic acids, alkyl-substituted phenyl tricarboxylic acids, and alkyl-substituted phenyl tetracarboxylic acids.

25. The digester additive formulation of claim 1, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, is a salt of phenyl tetracarboxylic acid.

26. A mixture comprising oven dried wood chips for use in a kraft process for making wood pulp, and the digester additive formulation of claim 1 , wherein the digester additive formulation is present in the mixture in an amount of from 0.001% by weight to 8% by weight, based on the weight of the oven-dried wood chips.

27. A wood pulp mixture for use in a kraft process for making wood pulp, the mixture comprising wood chips, white liquor, dilution water, and the digester additive formulation of claim 1.

28. The wood pulp mixture of claim 27, wherein the digester additive formulation is present in the mixture in an amount of from 0.001% by weight to 8% by weight, based on a dry weight of the wood chips.

29. A method comprising:mixing together wood chips, white liquor, dilution water, and the digester additive formulation of claim 1 , to form a wood pulp mixture.

30. The method of claim 29, wherein the phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, are first mixed together to form the digester additive formulation, before the digester additive formulation is mixed with the wood chips, the white liquor, and the dilution water.

31. The method of claim 29, comprising first mixing together the wood chips, the white liquor, and the dilution water, to form a precursor mixture, and then adding separately the phenyl tetracarboxylic acid or a derivative or salt thereof, and a macromolecule polymer, so that the digester additive formulation is formed in-situ, in the precursor mixture, to form the wood pulp mixture.

32. The method of claim 29, further comprising forming a wood pulp from the wood pulp mixture, and forming a paper from the wood pulp, according to a kraft process.

33. The method of claim 32, wherein the method improves pulp viscosity of the wood pulp, improves yield of the wood pulp, and reduces rejects in forming the wood pulp, when compared with the same method but carried out without the use of the digester additive formulation.

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