KR20080006582A - Improved composition and processes for paper production - Google Patents

Abstract

Compositions and processes that preserve and enhance the brightness and improve color of pulp or paper when applied during different stages of the papermaking process are identified. The composition and method maintains and/or enhances brightness, prevent yellowing, and enhances the performance of paper products. Used in combination with optical brighteners and/or chelants the described agents produce a synergistic effect not previously identified in the paper process.

Description

IMPROVED COMPOSITION AND PROCESSES FOR PAPER PRODUCTION

The present invention relates to compositions and processes for improving whiteness and optical properties in pulp and paper production, preventing the reduction in whiteness and improving resistance to thermal yellowing. More particularly, the present invention relates to compositions, which effectively improves the whiteness and optical properties of paper products and increases the thermal stability of paper products, either by themselves or in combination with optical brighteners.

Pulps produced by mechanical or chemical pulping methods have colors ranging from dark brown to creamish, depending on the type of wood and the fiber decomposition process used. The pulp is bleached to produce a variety of white paper products.

Bleaching is the removal or replacement of light absorbing materials found in unbleached pulp. In the bleaching of mechanical pulp, the purpose is to decolor the pulp without increasing the solubility of lignin. Reducing bleaching agents (eg hydrosulfite sodium) or oxidizing bleaching agents (eg hydrogen peroxide) are usually used. Bleaching is often a multistep process. Bleaching of chemical pulp is an extension of delignification that begins in the digestion step. Bleaching is often a multi-step process, which may include chlorine peroxide bleaching, oxygen-alkali talignin, and bleaching peroxide.

Decolorization by most of the thermal aging results in sulfidation and whiteness reduction in the final paper products at various stages of the paper production processes applying bleached pulp. In the industry, chemicals such as bleaching agents and optical brighters are important developments that improve the optical properties of the final paper or paper products. However, to date, the results have been more satisfactory, and economic losses due to discoloration and sulfidation present significant industry challenges for the industry. Thus, there remains a need for a successful and practical solution to the loss of whiteness of pulp and paper and to unwanted sulfidation.

The present invention provides compositions and methods for improving and stabilizing whiteness in paper making processes and for improving resistance to sulfidation.

In one aspect, the present invention is a method of providing a bleached pulp material having improved whiteness and improved resistance to thermal sulfidation, the method comprising the steps of: (1) providing a bleached pulp material; And (2) contacting the bleached pulp material with an effective amount of one or more reducing agents.

In another aspect, the present invention is a method of making a paper product having improved whiteness and resistance to thermal sulfiding, the method comprising the steps of: (1) providing bleached pulp; (2) forming an aqueous stock suspension comprising bleached pulp; (3) dewatering the stock suspension to form a sheet; (4) drying the sheet to form the paper product, wherein an effective amount of one or more reducing agents is added to the bleached pulp, to the stock suspension or onto the paper.

In another aspect, the invention is a method of preventing whitening and sulfidation of bleached pulp materials during storage, wherein the method comprises an effective amount of one or more reducing agents and optionally one or more chelants and one or more poly Adding carboxylates to the bleached pulp material.

In another aspect, the invention is a bleached pulp material comprising a mixture of bleached pulp and an effective amount of one or more reducing agents, where the bleached pulp material is further compared to similar pulp not treated with the reducing agents. High whiteness and improved resistance to thermal sulfidation.

Applicants also note that reducing agents combined with chelate compounds effectively increase the whiteness of paper products and furthermore reducing agents combined with optical brighteners increase the effect of optical brighteners and improve color schemes. . Thus, in further aspects, the present invention provides bleached pulp materials having higher whiteness, increased resistance to thermal sulfiding and improved color schemes using reducing agents combined with chelating compounds and / or optical brighteners. That's how.

Reducing agents, optical brighteners and chelating compounds can be used alone or in combination with known additives to increase the quality of the desired paper product.

The present invention provides an improved process for paper and paper products that exhibits high optical whiteness. Whiteness stabilization, color enhancement and whiteness increase for thermal sulfidation of bleached pulp and paper products made from bleached pulp are one or more reductions in pulp, paper, paperboard or tissue as defined herein anywhere in the paper manufacturing process. Can be achieved by adding agents

Whiteness is a term used to describe the degree of whiteness of a pulp or paper, which is based on the reflectance of blue light (457 nm) from paper and has a complete whiteness of 0% (perfect black) to 100% (about 96%). Relative to the MgO criterion). "Thermal whiteness loss" is the whiteness loss (non-photochemical whiteness loss) in paper and pulp under the influence of time, temperature and moisture. “Whiteness loss during storage” is thermal whiteness loss over time under storage conditions.

Sulfurization (whiteness reversal) of bleached pulp material is a decrease in whiteness over time of related materials made from bleached pulp, paper, paperboard, paper tissue and bleached pulp.

The reducing agents described herein are suitable for use with any bleached pulp materials used in paper making processes and any paper product made from bleached pulp. As used herein, "bleached pulp material" means bleached pulp and paper products made from bleached pulp, including paper, paperboard, tissue, and the like.

Reducing agents according to the present invention include chemicals capable of converting functional groups in the bleached pulp from a higher oxidation category to a lower one. Benefits of this conversion include increased whiteness stability in paper machines and increased performance of optical brighteners.

In one embodiment, the reducing agent is sulfite, bisulfite, metabisulfite (pyrosulfite), sulfoxylates, thiosulfate , Dithionite (hydorsulfite), polythionates, formamidinesulfinic acid and salts and derivatives thereof, formaldehyde bisulfite adduct (formaldehyde bisulfite adduct) and other aldehyde bisulfite adducts, ethers of sulfinamides and sulfinic acid, ethers of sulfenamides and sulfenic acid , Sulfamides, phosphines, phosphonium salts, phosphites, and thiophosphites.

As used herein, “sulfites” refer to dibasic metal salts of sulfite, H ₂ SO ₄ , which are alkali and alkyl such as sodium sulfite (Na ₂ SO ₃ ), calcium sulfite (CaSO ₃ ), and the like. Lito metal salts.

"Bisulfites" refer to monobasic metal salts of sulfite, H ₂ SO ₄ , which are alkali and alkaline earth groups 1 such as sodium bisulfite (NaHSO ₃ ), magnesium bisulfite (Mg (HSO ₃ ) _2, etc.). Basic salts.

“Sulfoxylates” means salts of sulfoxylic acid, H ₂ SO ₂ , including sulfoxylate zinc (ZnSO ₃ ) and the like.

"Metabisulfites (pyrosulfites)" means salts of pyrosulfurous acid, H ₂ S ₂ O ₅ , including sodium metabisulfite (Na ₂ S ₂ O ₅ ) and the like.

"Ciosulfates" means salts of thiosulfurous acid, H ₂ S ₂ O ₃ , including thiosulphate potassium (Na ₂ S ₂ O ₃ ) and the like.

"Polyionates" include dithionic acids such as trithionate sodium (Na ₂ S ₃ O ₆ ), dithionate sodium, Na ₂ S ₂ O ₃ , Mean salts of polythionic acid, H ₂ S _n O ₆ (n = 2-6), including salts of H ₂ S ₂ O ₆ , and the like.

"Dioneites (hydrosulfites)" are DCs that include sodium dithionite (hydro sulfite) (Na ₂ S ₂ O ₄ ), dissionite magnesium (MgS ₂ O ₄ ), and the like. Salts of owner's acid (hydrosulfite, hyposulfite), H ₂ S ₂ O ₄ , and the like.

"Formamidine sulfinic acid (FAS)" means a compound of formula H ₂ NC (= NH) SO ₂ H and salts and derivatives thereof, including sodium salt H ₂ NC (= NH) SO ₂ Na.

"Aldehyde bisulfite adducts" means metal salts wherein R ₁ CH (OH) SO ₃ H and R ₁ are selected from alkyl, alkenyl, aryl and arylalkyl. Representative aldehyde bisulfite adducts include formaldehyde bisulfite adduct HOCH ₂ SO ₃ Na and the like.

"Sulfinamides and ethers of sulfinic acid" mean compounds of the formula R ₁ -S (= 0) -R ₂ , wherein R ₁ is defined above and R ₂ is selected from OR ₃ and NR ₄ R ₅ , Wherein R ₃ -R ₅ are independently selected from alkyl, alkenyl, aryl and arylalkyl. Representative sulfinamides include ethylsulfindimethylamide (CH ₃ CH ₂ S (= 0) N (CH ₃ ) ₂ ) and the like.

"Esters of sulfenamides and sulfenic acids" mean compounds of the formula R ₁ -SR ₂ , wherein R ₁ and R ₂ are defined above. Representative sulfenamides include ethylsulfendimethylamide (CH ₃ CH ₂ SN (CH ₃ ) ₂ ) and the like.

"Sulfamides" mean compounds of the formula R ₁ -C (= S) NR ₄ R ₅ , wherein R ₁ , R ₄ and R ₅ are defined above. Representative sulfamides include CH ₃ CH ₂ C (═S) N (CH ₃ ) ₂ and the like.

"Phosphines" refer to phosphines, derivatives of PH ₃ , phosphines of the formula R ₆ R ₇ R ₈ P which are normally organic substituted, wherein R ₆ -R ₈ are independently H, alkyl, Alkenyl, aryl, arylalkyl and NR ₄ R ₅ , wherein R ₄ and R ₅ have been defined above. Representative phosphines include (HOCH ₂ ) ₃ P (THP) and the like.

"Phosphites" means derivatives of phosphorous acid, P (OH) ₃ , comprising phosphites of the organic substituted formula (R ₃ O) (R ₄ O) (R ₅ O) P, wherein R ₃ -R ₅ is defined above. Representative phosphites include (CH ₃ CH ₂ O) ₃ P and the like.

"Ciophosphites" are derivatives of phosphorousious acid, HSP (OH) ₂ , which include thiophosphites of the organic substituted formula (R ₃ O) (R ₄ O) (R ₅ S) P Where R ₃ -R ₅ are defined above. Representative ciophosphites include (CH ₃ CH ₂ O) ₂ (CH ₃ CH ₂ S) P and the like.

"Phosporium salts" means organic substituted phosphines of the formula R ₁ R ₂ R ₃ R ₄ R ₅ P ⁺ X ^- wherein R ₁ and R ₄ -R ₅ are defined above and X is defined as Organic or inorganic anions. Representative phosphonium salts _{(HO 2 CCH 2 CH 2)} 3 P + HCl - , and the like _{(THP), [(HOCH 2} ) 4 P +] 2 (SO 4) 2- (BTHP).

"Alkenyl" means a monovalent group derived from a straight or branched hydrocarbon having at least one carbon-carbon double bond by removal of one hydrogen atom. "Alkenyl may be unsubstituted or substituted with one or more groups selected from amino, alkoxy, hydroxy and halogen.

"Alkoxy" means an alkyl group where one oxygen atom is attached to a portion of the parent molecule. Representative alkoxy groups include methoxy, ethoxy, propoxy, butoxy and the like. More preferred are methoxy and ethoxy.

"Alkyl" means a monovalent group derived from a hydrocarbon saturated with a straight or branched chain by the removal of one hydrogen atom. Alkyl may or may not be substituted with one or more groups selected from amino, alkoxy, hydroxy and halogen. Representative alkyl groups include methyl, ethyl, n- and iso-propyl, n-, sec-, iso- and tert-butyl and the like.

"Alkylene" means a divalent group derived from a saturated hydrocarbon in a straight or branched chain by the removal of two hydrogen atoms, for example methylene, 1,2-ethylene, 1,1-ethylene, 1,3-propylene, 2,2-dimethylpropylene, and the like.

"Amino" means a group of the formula -NY ₁ Y ₂ , wherein Y ₁ and Y ₂ are independently selected from hydrogen, alkyl, alkenyl, aryl and arylalkyl. Representative amino groups include amino (-NH ₂ ), methylamino, ethylamino, isopropylamino, diethylamino, dimeltylamino, methylethylamino and the like.

"Aryl" means aromatic carbocyclic radicals and heterocyclic radicals having about 5 to about 14 ring atoms. Aryl may be substituted or unsubstituted with one or more groups selected from amino, alkoxy, hydroxy and halogen. Representative aryls are phenyl, naphthyl, phenanthryl, anthracyl, pyridyl, furyl, pyrrolyl, quinolyl, thienyl, Thiazolyl, pyrimidyl, indolyl, and the like. "Arylalkyl" means an aryl group in which an alkylene group is attached to a parent molecule. Representative arylalkyl groups include benzyl, 2-phenylethyl, and the like.

"Halo" and "halogen" mean chlorine, fluorine, bromine and iodine.

"Salt" means a metal, ammonium, substituted ammonium or phosphonium salt of an inorganic or organic anionic counterion. Representative metals include sodium, lithium, potassium, calcium, magnesium, and the like. Representative anionic counterions include sulfites, bisulfites, sulfoxylates, metabisulfites, thiosulfates, polycionates, hydrosulfites, formamidinesulfinates, and the like.

In one embodiment, the reducing agent is selected from the group consisting of substituted phosphines, sulfites, bisulfites and metabisulfite.

In one embodiment, the reducing agent is sodium sulfite.

The process of the present invention can be implemented in a conventional paper making apparatus. Although paper making devices vary in operational and mechanical design, the processes for making paper in other equipment include common steps. Paper making typically includes a pulping step, a bleaching step, a stock making step, a wet end step and a dry end step.

In the pulping step, the individual cellulose fibers are separated from the cellulose source by mechanical or chemical action or by both action. Representative cellulose sources include trees and similar "tree" plants, beans, rice, cotton, straw, flax, abaca, hemp, bagasse, lignin-containing Plants, and the like, as well as, but not limited to, raw and recycled paper, paper tissues and paperboard, and the like. These pulp can be groundwood (GWD), bleached groundwood, thermomechanical pulps (TMP), bleached thermomechanical pulps, chemi-thermomechanical pulps (CTMP), bleaching Chemical-thermomechanical pulp, deinked pulp, kraft pulp, bleached kraft pulp, sulfurous acid pulp, and bleached sulfite pulp. Regeneration pulp may or may not be bleached in the regeneration step, but it is assumed that regeneration pulp is bleached from the beginning. Some of the pulp described above that are not previously provided in the bleaching step can be bleached to provide a bleached pulp material as described herein.

In one embodiment, the bleached pulp material is virgin pulp, recycled pulp, kraft, sulfite, mechanical pulp, combinations of these pulp, recycled paper, paper tissue, and combinations of pulp or pulp listed above. It is selected from the group consisting of papers made from.

A further advantage of the present invention is that it is possible to replace higher cost kraft with lower cost mechanical pulp in print grade kraft-machined paper. The use of chemistry and the methods described herein increases the whiteness and stability to sulfidation, thus allowing greater use of mechanical pulp, which entails cost reduction without loss of quality of the final paper product.

In the stock preparation step the pulp is suspended in water. Brightening agents, dyes, pigments, fillers, antibacterial agents, defoamers, pH adjusting agents and drainage acid may also be added to the stock at this stage. As the term is used in this disclosure, "stock preparation" includes processes such as dilution, screening and cleaning of stock suspensions that occur at the formation line of the web.

The wet end step of the paper making process involves depositing a stock suspension or pulp feed onto a wire or felt of a paper making machine to form a web of subsequent fibers, draining the web and curing the web (“pressing”). ) To form a sheet. Any paper making machine known in the art is suitable for use in the process of the present invention. Such machines may include cylinder machines, fourdrinier machines, twin wire forming machines, tissue machines, and the like and variations thereof.

In the dry end stage of the paper making process, the web is dried and subjected to additional processes such as spray coating, printing, cutting, wrinkling with size pressing, calendering, surface modifiers, and the like. Can be provided. In addition to the size press and calendar waterboxes, the dried paper may be coated by spray coating using a sprayboom.

Applicants also note that reducing agents in combination with chelating compounds effectively increase the whiteness of the paper product by increasing the thermal stability of the pulp and the reduction of chromophoric structures in the pulp.

In one embodiment, one or more chelating compounds are added to the bleached pulp or paper product. Suitable chelating compounds according to the present invention include compounds capable of forming colored products as constituents of the pulp and chelating transition metals which promote the color-forming reaction in bleached pulp or paper products.

In one embodiment, the chelate compound consists of organic phosphonates, phosphates, carboxylic acids, dithiocarbamates, salts of any of the previous elements, and any combination of these It is a compound selected from the group which becomes.

"Organic phosphonates" refer to organic derivatives of the phosphonic acid, HP (O) (OH) ₂ , which include a single CP bond, HEDP (CH ₃ (OH) (P (O)) (OH) ₂ ), 1-hydroxy-1,3-propanylbis-phosphonic acid ((HO) ₂ P (O) CH (OH) CH ₂ CH ₂ P (O) (OH) ₂ )) yl Can be; More preferably comprising a single CN bond adjacent to (near) the CP bond, DTMPA ((HO) ₂ P (O) CH ₂ N [CH ₂ CH ₂ N (CH ₂ P (O) (OH) ₂ ). ) ₂ ] ₂ ), AMP (N (CH ₂ P (O) (OH) ₂ ) ₃ ), PAPEMP ((HO) ₂ P (O) CH ₂ ) ₂ NCH (CH ₃ ) CH ₂ (OCH ₂ CH ( CH ₃ )) ₂ N (CH ₂ ) ₆ N (CH ₂ P (O) (OH) ₂ ) ₂ ), HMDTMP ((HO) ₂ P (O) (CH) ₂ ) ₂ N (CH ₂ ) ₆ N (CH ₂ P (O) (OH) ₂ ) ₂ ), HEBMP (N (CH ₂ P (O) (OH) ₂ ) ₂ CH ₂ CH ₂ OH), and the like.

“Organic phosphates” have a single CP bond and include phosphoric acid, P (O) (OH, including triethanolamine tri (phosphate ester) (N (CH ₂ CH ₂ OP (O) (OH) ₂ ) _3, etc. ) Organic derivatives of ₃ ).

"Carboxylic acids" means an organic compound having one or more carboxylic group (s), -C (O) OH, more preferably a single CN bond adjacent to (near) a C-CO ₂ H bond EDTA ((HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CO ₂ H) ₂ ), DTPA ((HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CO ₂ H) CH ₂ CH ₂ N (CH ₂ CO ₂ H) ₂ ), and the like and aminocarboxylic acids such as alkali and alkaline earth salts thereof.

"Dithiocarbamates" include monomeric dithiocarbamates, polymeric dithiocarbamates, polydiallylamine dioxycarbamates, 2,4,6-trimercapto-1,3,5- Triazine (2,4,6-trimercapto-1,3,5-triazine), disodium ethylenebisdithiocarbamate, disodium dimethyldithiocarbamate and the like.

In one embodiment, the chelate compound is phosphonate.

In one embodiment, the phosphonate is diethylene-triamine-pentamethylene phosphonic acid (DTMPA) and salts thereof.

In one embodiment, the chelate compound is a carboxylic acid.

In one embodiment, the carboxylate is selected from diethylenetriaminepentaacetic acid (DTPA) and salts thereof and ethylenediaminetertraacetic acid (EDTA) and salts thereof.

Applicants have also found that reducing agents used in combination with optical brighteners (“OBA's”) increase the effect of optical brighteners (OBA). Reducing agents also improve color combination. This allows for a reduction in the amount of OBA's and brighteners, such as blue dyes, required to achieve equivalent whiteness and color. Replacing some OBAs and dyes with reducing agents reduces the cost of production and reduces the overall amount of OBAs and dyes present while pulp and paper producers maintain acceptable whiteness levels in paper products and achieve target colors. Make it possible to reduce. In some cases, it is possible to completely remove the dyes and maintain the color.

Thus, in another embodiment, one or more optical brighteners ("OBA's") are added to the bleached pulp or paper product.

"Optical brighteners" are fluorescences that absorb ultraviolet light and re-emit ultraviolet light absorbed at higher frequencies in the visible spectrum (blue) to add a white, bright appearance to the paper sheet when added to the stock feed. Dyes or pigments. Representative optical brighteners include azoles, biphenyls, coumarins; Furans, such as Eccobrite® and Eccwhite® compounds available from Eastern Color & Chemical Co. (Providence, RI); Ionic brighteners including anion, cation, and anion (neutral) compounds; Naphthalimides; Pyrazenes; Leucophor® range of optical brighteners available from Clariant Corporation (Muttenz, Switzerland), and substituted (eg sulfonated) stilbenes such as Tinopal® available from Ciba Specialty Chemicals (Basel, Switzerland) stilbene); Salts of these compounds, including but not limited to alkali metal salts, alkaline earth metal salts, transition metal salts, organic salts and ammonium salts of such brightening agents; And combinations of one or more of the foregoing agents.

In one embodiment the optical brighteners are selected from the group of disulfonated, tetrasulfonated and hexasulfonated Tinopal® OBAs.

The dosage of reducing agents, chelating compounds and / or optical brighteners is the amount necessary to achieve the desired whiteness and resistance to sulfidation of the bleached pulp or paper product made from the bleached pulp, the chelate compound or optical brightener, It can be readily determined by one of ordinary skill in the art based on the characteristics of the pulp or paper being processed and the method of application.

The effective amount of reducing agent added to the bleached pulp or paper product is the amount of reducing agent that improves the whiteness and thermal sulfidation of the pulp or paper as compared to the pulp or paper not treated with the sulfur source agent. Methods of determining whiteness and resistance to thermal sulfiding are described herein.

Typically, from about 0.005 to about 2, more preferably from about 0.05 to 0.25 weight percent of reducing agent based on oven-dried pulp is added to the bleached pulp or paper product.

In a typical application, from about 0.001 to 1, more preferably from about 0.01 to about 0.02 percent by weight of dithiocarbamates chelate compound based on oven-dried pulp is added to the bleached pulp or paper product.

Optical brighteners are typically added from about 0.005 to about 2, more preferably from 0.05 to 1 weight percent of optical brightener based on oven-dried pulp.

Reducing agents, chelating compounds and / or optical brighteners may be added to the bleached pulp or paper at any point in the paper making or tissue making process. Representative addition points include (a) to the pulp feed in the atmosphere chest; (b) to the pulp after the bleaching step in a storage, blending or transfer chest; (c) to pulp after bleaching, washing and dehydration after cylinder or flash drying; (d) after or before cleaners; (e) before or after a fan pump to the paper machine headbox; (f) paper machine white water; (g) in silos or save all; (h) to a press section using, for example, a size press, coater or spray bar; (i) in a drying section using, for example, a size press, coater or spray bar; (j) on a calendar using a wafer box; And / or on paper in an off-machine coater or size press and / or in a (l) curl control unit.

The exact point at which reducing agents, chelating compounds and / or optical brighteners should be added will depend on the particular equipment deployed, the exact process conditions used and the like. In some cases, the reducing agents, chelating compounds and / or optical brighteners are applied at one point in the paper making process, for example, pulp or wet sheet (before the dryer) and the remaining amount is at a subsequent point. For example, it is added to the size press.

The application may be by any means conventionally used in paper making processes, in which a portion of the reducing agent, chelating compound and / or optical brightener is one point in the paper making process, for example pulp. And "split-feeding" added to or at the wet sheet (before the dryers) and added at the point where the remaining part is followed, for example in a size press.

Chelating compounds and / or optical brighteners may be added to the bleached pulp or paper product before, after or simultaneously with the reducing agent. Optical brighteners and / or chelate compounds may also be formulated with reducing agents.

In one embodiment, one or more reducing agents and one or more optical brighteners are mixed in a surface sizing solution and applied to a size press.

In one embodiment, the reducing agent is added to the bleached pulp after the bleaching step in the storage, mixing or transfer chest.

At these various points, reducing agents, chelating compounds and / or optical brighteners may also contain retention aids, sizing aids and solutions, starches, precipitated calcium carbonate, basic calcium carbonate Or other clays or fillers, and brightening additives such as lightening agents or additives that are commonly used in paper making.

In one embodiment, the reducing agents, chelating compounds and / or brighteners are one or more partially neutralized polycarboxylic acids, more preferably polyacrylic acid (CH ₃ CH (CO ₂ H). ) [CH ₂ CH (CO ₂ H)] _n CH ₂ CH ₂ CO ₂ H, where n is from about 10 to 50,000. The polycarboxylic acid is used in alkali such as sodium hydroxide. Can be neutralized to a target pH (typically 5-6 as discussed below).

In one embodiment, the present invention is a formulation comprising one or more chelating compounds, one or more reducing agents and one or more polycarboxylic acids. The formulation preferably has a pH of about 4-7, more preferably 5-6.

In one embodiment, the invention is a formulation comprising one or more reducing agents and one or more optical brighteners and additionally one or more chelating compounds or one or more polycarboxylates, or combinations thereof. The formulations according to this example preferably have a pH of about 7-11, more preferably a pH of about 9-10.

Reducing agents, chelating compounds and optical brighteners and polycarboxylates can be used in addition to other additives, which enhance one or more properties of the final paper product or assist in the process of producing the paper itself. It is commonly used in paper making to do both, or both. Such additives can generally be classified into functional additives or control additives.

Functional additives are additives that are typically used to enhance or impart certain particular desired properties to the final paper product and include, but are not limited to, brightening agents, dyes, fillers, sizing agents, starches, and adhesives.

Control additives, on the other hand, are additives that are mixed during the paper production process to improve the overall process without significantly affecting the physical properties of the paper. Control additives include biocides, retention agents, defoamers, pH control agents, pitch control agents, and drainage aids. Paper and paper products made using the process of the present invention contain one or more functional additives and / or control additives.

Pigments and dyes impart color to the paper. Dyes include organic compounds, wherein the organic compounds include conjugated double bond systems; Azo compounds; Metal azo compounds; Anthraquinones; Triaryl compounds such as triarylmethane; Quinoline and related compounds; Acid dyes (anionic organic dyes containing sulfonate groups, used with organic materials such as aluminum sulfate); Base dyes (cationic organic dyes containing amine functional groups); And direct dyes (acid-type dyes having high molecular weight and specific, direct affinity for cellulose); As well as combinations of the suitable dye compounds listed above. Pigments are finely divided white or colored metals. Pigments commonly used in the paper making industry are clays, calcium carbonates and titanium oxides.

Fillers are added to the paper to increase opacity and whiteness. Fillers include calcium carbonate (calcite); Precipitated calcium carbonate (PCC); Calcium sulfate (including various hydration forms); Calcium aluminate; Zinc oxides; Magnesium silicates such as talc; Titanium dioxide (TiO ₂ ) such as anatase or rutile; Clay, or kaolin, consisting of hydrated SiO ₂ and Al ₂ O ₃ ; Synthetic clay; Mica; Vermiculite; Weapon aggregates; Perlite; sand; Gravel; Sandstone; Glass beads; Aerogels; Xerogels; Seagel; Fly ash; Alumina; Microspheres; Hollow glass spheres; Porous ceramic spheres; Cork; Seeds; Lightweight polymers; Xonotlite (calcium silicate gel crystals); Pumice; Exfoliated rock; Waste concrete products; Hydroponic cement particles partially or unhydrated; And diatomaceous earth, as well as combinations of these compounds.

Sizing agents are added to the paper during the manufacturing process to aid in the growth of resistance to penetration of liquids through the paper. The sizing agents may be internal sizing agents or external (surface) sizing agents, and may be hard-sizing, slack-sizing, or both methods. In more detail, sizing agents include rosins; Rosin precipitated with aluminum sulfate (Alum, Al ₂ (SO ₄ ) ₃ ); Abiate acid cognates such as abietic acid and neoabietic acid and levopimaric acid; Stearic acid and stearic acid derivatives; Ammonium zirconium carbonates; Silicone-containing compounds such as RE-29 available from Silicon and GE-OSI, Sm-8715 available from Dow Cornig Corporation (Midland, MI); The general structural formula is CF ₃ (CF ₂ ) _n R where R is an anion, cation, or other functional group such as Gortex; Alkylketene dimers (AKDs) such as Aquapel 364, Aquapel (I 752, Heron) 70, Hercon 79, Precise 787, Precise 2000, and Precise 3000, all available from Hercules, Incorporated (Willmington, DE). ; And alkyl succinic anhydrides (ASA); Emulsions of ASA or AKD formed with cationic starch; ASA mixed with aluminum sulfide; Starch; Hydroxymethyl starch; Carboxymethylcellulose (CMC); Polyvinyl alcohol; Methyl cellulose; Alginates; Waxes; Wax emulsions; And combinations of the above sizing agents.

Starch has many uses in paper making. For example, starch functions as a retention agent, dry-strength aid and surface sizing agent. Starches are amylose; Amylopectin; Starches having various amounts of amylose and amylopectin, such as 25% amylose and 75% amylopectin (corn starch) and 20% amylose and 80% amylopectin (potato starch); Starches processed by enzymes; Hydrolyzed starches; Heat treated starches known in the art as "pasted starchs"; Cationic starches that react with starch with a tertiary amine to form salts of quaternary ammonium; Anionic starches; Ampholytic starches (having both cationic and anionic functions); Cellulose and cellulose derived compounds; And combinations of these compounds.

The method of the present invention produces paper products with bright surfaces. Moreover, the new composition better protects the paper from long-term discoloration during normal use of the paper.

In the following, it may be better understood by the description according to the following examples, which are presented for illustrative purposes only and are not intended to limit the scope of the invention.

TABLE 1

Representative compositions (moisture not included)

Component %component Composition A DTMPA 7.6 Polyacrylate sodium 3.5 NaOH 1.5 Metabisulfite sodium 26.6 Composition B DTMPA 9.0 NaOH 3.6 Metasulfite sodium 27 Composition C DTMPA 6.0 DTPA 4.1 NaOH 1.5 Metasulfite sodium 30 Composition D DTMPA 5.0 DTPA 5.5 NaOH 16.7 Metasulfite sodium 7.7 Composition E DTMPA 7.4 NaOH 5.5 Metasulfite sodium 16.7 FAS 7.7 Composition F DTMPA 4.2 NaOH 2.8 Metasulfite sodium 19.9 THPS 9.8 DTPA 4.1 NaNO ₂ 1.3 Composition G DTPA 2.9 Polyacrylate sodium 1.0 NaOH 1.3 Metasulfite sodium 30.0

Example

In these examples, sufficient 50% water soluble sodium hydroxide was added to achieve a suitable pH for the agent or composition to be tested. All percentages in these examples are given in weight percent based on the dried pulp.

In the examples, the following terms will have the meaning indicated. Br is ISO whiteness R457 (TAPPI 525); Ye is R313 sulphide; Im Br is R457 whiteness after application; TA Br is R457 whiteness after thermal aging; TA loss is loss in whiteness after thermal aging; % Inh. Inhibition:% Inh. = 100-100 * (ImBr-TABr) / (ImBr-TABr) _control ; WI is E313 whiteness: TMP is thermomechanical pulp; CTMP is a chemical-thermodynamic pulp; RMP is a refiner machine pulp; OBAs are optical brighteners; FAS is formamidine sulfinic acid; TCP is (HOCH ₂ CH ₂ ) ₃ PHCl, tris-carboxyethylphosphonium hydrochloride; BTHP is [(HOCH ₂ ) ₄ P] ₂ (SO ₄ ), tetra-hydroxymethylphosphonium sulfate; THP is (HOCH ₂ ) ₃ P, tris-hydroxymethylphosphine; EDTA is (HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CO ₂ H) ₂ , ethylenediaminetetraacetic acid; DTPA is (HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CO ₂ H) ₂ , diethylenetriaminepentaacetic acid; DTMPA is H ₂ O ₃ PCH ₂ N [CH ₂ CH ₂ N (CH ₂ PO ₃ H ₂ ) ₂ ] ₂ , diethylene-triamine-pentamethylenephosphonic acid; And DTC is dimethyldithiocarbamate sodium.

process

Handsheets are made of bleached pulp and later used in experiments, in which the reducing agents are either before drum-drying or after drum-drying (temperature during drum drying: 100 ° C.). Before or after the press). The third option is a split-feed application. Surface sizing applications were run one or more times in a drum dryer.

The amount of agent or composition solution tested was determined based on the dry weight of the pulp sample. The agent or composition solutions were applied in an aqueous solution, as uniformly as possible, using a rod. Test sheets were dried using a laboratory drum dryer under uniform conditions (once) and presented in accelerated aging tests as described below after measuring whiteness.

Whiteness Inversion Experiments (Thermal Aging , paper):

The 3 × 9 cm cut samples of test sheets were immersed in an underwater bath at 70 ° C. at 100% humidity for about 3 days. The samples were equilibrated in a room of constant humidity before measuring the whiteness.

Whiteness Inversion Experiments (Thermal Aging Pulp):

Pulp samples were sealed in plastic bags (10% concentration, 5 g pulp on o.d. basis) and submerged in a 70 ° C. underwater bath for 3-6 hours. Handsheets were prepared and equilibrated in a room of constant humidity before measuring whiteness.

Testing equipment:

Laboratory drum dryer.

"Elrepho 3000", "Technidyne Color Touch 2 (Model ISO)" or another instrument for measuring whiteness.

Hitachi F-4500 fluorescence spectrometer or another instrument for relative fluorescence intensity measurements.

Micropipette.

Surface Size Application Kit (Pad and Size 3-Application Rod)

Constant humidity room (23 ° C, 50% humidity)

Underwater Bath / Automatic Temperature Control System to Hold Floating Plastic Boxes with Paper Samples

100-mL application cuvette for the wet method.

Surface drying application process (surface Sizing ):

1. Make an 8 × 8-inch handsheet following the basic procedure. The target dry weight is 2.5 g. The wet handsheets are passed one cycle through the drum dryer.

2. Cut the sheets into four small squares (approximate mass of 0.625 g each).

3. Using a scotch tape longer than the side of the sheet, stick one side of a smaller rectangle (test sheet) to the glass pad.

4. Application The rod is placed on Scotch tape and 0.2 ml of the mixture is applied onto the tape against the rod using a micropipette.

5. The agent solution is applied by distributing on a tape covering the entire test sheet.

6. Use a rod to quickly drain the solution from the tape over the sheet so that the reducing agent compound solution is applied over the entire sheet.

7. Drum dry the test sheet and equilibrate at room temperature.

8. Measure the whiteness and sulfidation.

Dry Surface Application Process (Surface Sizing How to soak):

1. Make an 8 × 8-inch handsheet following the basic procedure. The target dry weight is 2.5 g. The wet handsheets are passed one cycle through the drum dryer.

2. Cut a piece of sheet into 1 / 8th (0.31g).

3. In 50 ml test tubes, pre-prepared (if necessary) starch solutions and reducing agent compound solutions are prepared based on a predetermined pick up rate and target dose.

4. Insert a piece of paper into the solution for 10 seconds, drip it for 35 seconds, and then pass it through the press.

5. Drum-dry the test sheet and equilibrate at room temperature.

6. Measure whiteness and sulfidation.

Wet end  Application process:

1. An 8 × 8-inch sheet is formed and dewatered using a press having two blowers at the bottom and one blotter at the top. The uniformity of the pressed sheet is about 40%.

2. The upper tack and the bottom main tack are removed from the sheet after the press.

3. With the bottom tack, the sheet is cut into four smaller test sheets of equal size (approximately dry weight of the sheet is 0.625 g).

4. The test sheet is pasted together with the front plate to the glass pad as described in "Dry Surface Application Procedure".

5. Solution 1 is applied as described in the dry surface application procedure.

6. After application, the test sheet is removed from the glass pad with the wet bottom tack, the tape is removed and the tack is separated from the test sheet. The blotter is abandoned.

7. The test sheet is then drum dried and equilibrated at room temperature.

Separate feed application process:

1. Following the basic procedure, an 8x8-inch sheet is made.

2. The sheet formed on the screen is then padded with four tacks.

3. The sheet together with the tacks is then couched using a heavy metal roller. This process removes moisture from the sheet, increasing the uniformity of the sheet to about 20%.

4. The three upper tacks are removed from the sheet.

5. The sheet and one blotter are then removed from the screen and cut into four smaller pieces as described in "Wet end application process".

6. The sheets and tacks are then attached to the glass pads as described in "Wet end application process".

7. Solution 2 is applied as described in "Wet end application process".

8. The test sheet is then pressed into two tacks on each side.

9. After pressing, all the tacks are removed and the sheet is drum dried.

Solution 2 is then applied to the sheet, dried and measured as described in steps 3 to 8 of the “dry surface application process”.

Pulp Application Process:

Chemicals were added directly to the pulp (thin stock or thick stock) and mixed with the pulp in a sealed bag. During the pulp application for increasing OBA, the chemicals were added directly to the bleached kraft pulp at 20% uniformity, mixed into the pulp in sealed bags and held at 45-85 ° C. for 30 minutes. The pulp was diluted to 5% uniformity, OBA was added, mixed with the pulp, and the feed was held at 50 ° C. for 20 minutes. The feed was then diluted further and the handsheets were made following the basic procedure.

Test results

1. Mill Test ( Mill Trial )

Test data was collected from Sourthern Craft Mill. The table below provides sample data. In some tests, in size presses, with OBA in sizing solution, application of the product (Composition A) at 5 lb / t and higher dosages is accompanied by an improved color of the paper sheet (reflected to the reduced DE value). Steadily providing a 1.5-point whiteness increase. Reverting to standard mill conditions (without any penetration composition applied) resulted in a decrease in whiteness at the background level. This experiment was repeated three times.

TABLE 2

Test data: R457 whiteness, E313 whiteness, DE (ΔE) = square root [(L ₀ -L) ² + (a ₀ -a) ² + (b ₀ -b) ² ]

Time, h Input, lb / t Whiteness DE WI E313 0 0 94.5 1.99 142.24 0.58 0 94.5 1.61 144.95 1.17 0 94.5 1.83 143.34 1.75 0 94.5 1.93 143.52 2.33 0 95.25 1.52 146.66 2.92 4 95.25 0.71 150 3.5 4 95.5 0.89 148.29 4.08 4 95.5 0.88 148.4 4.67 5 96 0.76 149.46 5.25 5 96 0.72 149.84 5.83 6 96 0.44 152.6 6.42 8 96 0.44 156.01 7 8 96 0.35 154.15 7.58 8 95.75 0.4 154.92 8.17 10 96 0.52 152.24

Several compositions have been tested and provided good results in laboratory simulations of PM applications. Chemicals (compositions) not listed in Table 1 were applied in 40% solutions.

2. Reducing Agent: Meta  Sodium sulfite (30% solution)

TABLE 3

Surface application with mixed kraft-CTMP 1, headbox, starch (surface sizing solution) on both sides

# process Br One Control standard 94.34 2 0.27% Sodium Metasulfite 96.17

TABLE 4

Surface application with mixed kraft-CTMP 2, headbox, starch (surface sizing solution) on both sides

# process Br One Control standard 94.93 2 0.27% Sodium Metasulfite 95.63

TABLE 5

Mixed Craft-CTNP 3, Headbox

# process Br Gain over Control Benefits to OBA One Control standard 85.47 0 2 0.2% OBA 89.78 4.31 0 3 0.2% OBA + 0.2% Composition A 91.05 5.58 1.27 4 0.2% OBA + 0.054% Metasulfite Sodium 90.6 5.13 0.82 5 0.054% sodium metasulfite 86.31 0.84

TABLE 6

Finished (size) photocopy craft1, surface applied with starch (surface sizing solution) on one side

# process Br One Control standard 80.0 2 0.27% Sodium Metasulfite 80.50

TABLE 7

Finished (OBA sized) craft 2, surface applied with starch (surface sizing solution) on one side

# process Br One Control standard 94.78 2 0.27% Sodium Metasulfite 95.39

TABLE 8

Mechanical Processing-Craft2

# process Br One 0.2% metasulfite sodium 63.81 2 Drum-Dried (100 ° C) 62.28 3 Air-dried (23 ° C) 64.87

Table 3-8 shows the effect of reducing agent sulfite (methsulphite) sodium and whiteness increasing compositions on paper: reducing agents improve whiteness (Table 3-8) and partially compensate for whiteness loss in the dryer (Table 8). The chemical additionally improves the whiteness in the presence of OBA.

3. Than metasulfite  Other reducing agents.

Application in Model Surface Sizing Solutions with Starch

TABLE 9

TMP1

# process Br Ye One 0.2% THP 78.66 12.38 2 0.2% FAS 78.75 12.20 3 0.2% TCP 79.20 12.13 4 0.2% FAS 78.00 12.17 5 0.2% THP + 0.01% NaNO2 * 79.22 12.00 6 0.2% TCP + 0.01% NaNO2 * 79.11 12.12 7 Control standard 77.51 12.98

* Activator

TABLE 10

TMP1

# process Br Ye One Control standard 78.83 11.95 2 0.2% BTHP 81.06 10.90

TABLE 11

RMP

# process Br Ye One Control standard 76.75 13.57 2 0.2% BTHP 78.59 12.64 3 0.2% BTHP + 0.01% NaNO2 * 78.75 12.54 4 0.2% TCP + 0.01% NaNO2 * 78.38 12.70

* Activator

Table 9-11 shows the effects of metasulfite and other reducing chemicals such as FAS and phosphorus (III) compounds.

4. Chelate - Metasulfuric acid  Compositions

TABLE 12

Craft hardwood pulp 3, headbox

# process Br One 0% OBA2 87.56 2 0% OBA2 + 0.1% Composition C 88.07 3 20% OBA 92.08 4 20% OBA + 0.1% Composition C 92.80 5 40% OBA 93.05 6 40% OBA + 0.1% Composition C 93.60 7 100% OBA 93.43 8 100% OBA + 0.1% Composition C 93.95

TABLE 13

Activation of Mixed Craft-CTMP3, Optical Brightener

# process Br Gain over Control Synergy One Control standard 85.48 0 N / A 2 0.2% Composition C 86.79 1.35 N / A 3 0.2% OBA 89.7 4.21 N / A 4 0.35 OBA 90.73 5.22 N / A 5 0.1% Composition C 86.34 0.81 N / A 6 0.2% OBA + 0.2% Composition C 91.4 5.82 0.26 7 0.2% OBA + 0.1% Composition C 90.78 8.25 0.23 8 0.35% OBA + 0.2% Composition C 92.55 6.87 0.30 9 0.35% OBA + 0.1% Composition C 92.06 6.54 0.51

TABLE 14

Activation of optical brightener: kraft pulp 4 with OBA (0, 0.2%), composition C (0, 0.2%)

Br vs. (0,0) OBA1 C0, OBA0 78.24 0 C0, OBA0.2 79.74 1.5 C0.2, OBA0 80.43 2.19 C0.2, OBA0.2 82.53 4.29 Synergy 0.6

TABLE 15

Activation of optical brightener as measured by mixed kraft-CTMP1, headbox, fluorescence intensities:

Sample Fluorescence intensity Control standard 33746 0.2% Composition A 36149 0.35% OBA 106233 0.1% Composition A + 0.35% OBA 111609 0.2% Composition A + 0.35% OBA 116373 0.3% Composition A + 0.35% OBA 119845

TABLE 16

Craft headbox containing OBA, activation of optical brightener as measured by fluorescence intensities:

Sample Fluorescence intensity Control standard 87140 0.1% Composition A 106217 0.2% Composition A 108942 0.2% OBA 117513 0.2% Composition A + 0.2% OBA 120837

TABLE 17

Activation of optical brightener as measured by mixed feed (25% softwood, 40% hardwood kraft, 35% deinked), fluorescence intensities:

Sample Fluorescence intensity Control standard 57121 0.2% Composition A 57567 0.91% OBA 61339 0.2% Composition A + 0.6% OBA 60783 0.2% Composition A + 0.45% OBA 60868 0.2% Composition A + 0.3% OBA 59924

TABLE 18

TMP2

process Br Ye Control standard 78.43 12.06 0.2% Composition B 81.11 10.70 0.2% (sodium sulfite 3: DTPA1) 81.31 10.52

TABLE 19

TMP2

# process Br Ye One Control standard 78.83 11.95 2 0.05% FAS + 0.15% Composition B 81.35 10.72 3 0.2% BTHP 81.06 10.90 4 0.1% BTHP + 0.1% Composition B 80.28 11.32 5 0.2% (BTHP3: DTMP1) 81.40 10.73 6 0.2% Composition B 81.30 10.90

TABLE 20

Hardwood Craft 2

# process Br Ye One Control standard 88.41 3.51 2 0.2% Composition B 87.50 4.01 3 0.2% (Sodium Metasulfite 30: DTPA 5: DTMPA 5 88.16 3.56

TABLE 21

Craft 2 with surface sizing

# process Br Ye One 0.513% Composition A, Drum Dried 88.41 3.51 2 Drum dried 87.50 4.01 3 Air dried 88.16 3.56

Table 22

Craft 2 with surface sizing

# process Br One 0.2% Composition A, Drum Dried 88.31 2 Drum dried 87.76 3 Air dried 88.67

TABLE 23

Mechanical treatment-kraft pulp mixing, headbox feeding, wet end application

Br 0.1% sodium sulfite + 0.1% (DTMPA2: polyacrylate 1, 33% active molecules), drum dried 65.16 Drum dried 62.28 Air dried 64.87

TABLE 24

Craft 5, treated hand sheets, 100% humidity for 4 days at 70 ° C

# process Im Br TA Br TA loss One control 93.75 92.74 1.01 2 0.2% Composition A 94.41 93.57 0.84 3 0.5% Composition A 95.16 94.40 0.76 4 0.2% Composition G 94.23 93.41 0.82 5 0.5% Composition G 94.68 94.04 0.64

TABLE 25

Craft 5, treated hand sheets, 100% humidity for 4 days at 70 ° C

# process Im Br TA Br TA loss One control 93.42 92.13 1.29 2 0.2% OBA 94.20 92.76 1.44 3 0.2% Composition A + 0.2% OBA 95.05 94.59 0.46 4 0.2% Composition G + 0.2% OBA 94.89 94.39 0.50 5 0.5% Composition G 94.59 94.17 0.42

TABLE 26

Craft 2, 10% uniformity pulp, 3 hours at 70 ℃

# process Br One Original pulp (not exposed to heat) 88.05 2 Control standard (exposed to heat) 87.11 3 0.2% Composition A 87.99 4 0.2% Composition G 87.90 5 0.5% Composition A 87.94 6 0.5% Composition G 88.47

TABLE 27

Craft 2, 10% uniformity pulp, 6 hours at 70 ° C

# process Br One Original pulp (not exposed to heat) 88.67 2 Control standard (exposed to heat) 87.76 3 0.2% Composition A 88.31 4 0.2% Composition G 88.34 5 0.5% Composition A 88.61 6 0.5% Composition G 88.67

Tables 12-27 show the application of the compositions of reducing agents bound with chelate compound (s). Other combinations can be compared (all effectively). The formulations improve the long term whiteness stability of the paper against thermal aging (Table 24-27). This set of data also shows the activation of OBA by the compositions (Tables 12-14, 25). Application of the formulation enables the saving of the dosage of brightener. Tables 16 and 17 show the effect of the formulation on fluorescence.

5. Wet end  Apply: applied later OBA of Increased  Separation application to the pulp of the composition leading to performance.

Pulp application process for continuous OBA increase (80 ° C)

TABLE 28

Craft 6

# % Composition A % OBA Br Gain over Control One 0 0 86.78 0.00 2 0 0.5 88.70 1.92 3 0 0.25 88.22 1.44 4 0.5 0 88.05 1.27 5 0.5 0.5 91.04 4.26 6 0.50 0.25 89.38 2.60 7 0.25 0.25 90.55 3.77

TABLE 29

Craft 6

# % Composition G % OBA Br Gain over Control One 0 0 86.64 0.00 2 0.5 0.5 91.66 5.02 3 0.5 0.25 90.69 4.05 4 0.25 0.25 89.32 2.68 5 0 0.5 89.00 2.36 6 0.5 0 87.68 1.04

TABLE 30

Kraft 6, Optical Brightener Activation Measured by Three Fluorescent Groups

Sample Fluorescence intensity control 7871 0.5% Composition G 10370 0.5% OBA 128578 0.5% composition G, then 0.5% OBA 201199 0.25% Composition G, then 0.5% OBA 161354 0.5% composition G, then 0.25% OBA 157359 0.5% Composition A, then 0.5% OBA 191759

Tables 28-30 show the activation of OBA by prior application of the composition.

6. Wet end  Application: to composition DC carbamates  Introduction of low inputs.

Table 31

RMP, couch (wet end) applied with moisture

# % Composition A % DTC Br Ye One 0.257% 0.0025% 79.53 11.65 2 0.257% 0.00125% 79.73 11.93 3 0.184% 0.0025% 80.05 11.63 4 0.184% 0.00125% 79.98 11.51 Air dried 80.15 11.30 Drum dried 78.28 12.60

Table 32

RMP, surface sizing

# % Composition A % DTC Im Br Im Ye TABr TAYe % Inh. One 0.513% 0.0025% 87.74 3.98 86.24 4.46 31 2 0.513% 0.0050% 87.17 4.52 86.27 4.54 58 Drum dried 87.64 9.92 85.47 5.05

The data (Table 31-33) show the whiteness recovery and long term stabilization for the application of the proposed formulations.

While the invention has been described above in terms of representative or exemplary embodiments, these embodiments are not intended to be exhaustive or to limit the invention. Rather, the invention is intended to cover alternatives, modifications and equivalents as included in the spirit and scope of the invention as defined in the claims that follow.

Claims (24)

Iii) providing a bleached pulp material; And Ii) contacting the bleached pulp material with an effective amount of one or more reducing agents, thereby producing a bleached pulp material having increased whiteness and increased resistance to thermal sulfiding. The method of claim 1, further comprising contacting the bleached pulp material with one or more optical brighteners. The method of claim 1, further comprising contacting the bleached pulp material with one or more chelate compounds. The bleached pulp material according to claim 1, wherein the bleached pulp material is virgin pulp, recycled pulp, kraft pulp, sulfite pulp, mechanical pulp, any combination of the pulp, recycled paper, paper tissue, and any paper made of the pulp or combinations. Or bleached pulp material, characterized in that it is selected from the group consisting of paper products. The method of claim 1, wherein the reducing agent is sulfites, bisulfites, metabisulfites (pyrosulfites), sulfoxylates, thiosulfates, disionites (high drosulfites), poly Cyanates, formamidinesulfonic acid and salts and derivatives thereof, formaldehyde bisulfite adducts and other aldehyde bisulfite adducts, sulfinamides and ethers of sulfinic acid, sulfenamides and sulfonic acids A process for producing a bleached pulp material, characterized in that it is selected from the group consisting of ethers, sulfamides, phosphines, phosphonium salts, phosphites, and thiophosphites. 6. The method of claim 5, wherein said reducing agent is selected from the group consisting of substituted phosphines, sulfites, bisulfites and metasulfites. 7. The method of claim 6, wherein said reducing agent is sodium bisulfite. 4. The chelating compound of claim 3, wherein said chelate compound is selected from the group consisting of organic phosphonates, phosphates, carboxylic acids, disocarbamates, salts of any of the preceding components, and combinations thereof. A process for producing a bleached pulp material, characterized in that the bleached pulp material. The method according to claim 8, wherein the chelate compound comprises diethylene-triamine-pentamethylene phosphonic acid (DTMPA) and salts thereof, diethylenetriaminepentaacetic acid (DTPA) and salts thereof and ethylenediaminetetraacetic acid ( EDTA) and salts thereof, and a method for producing bleached pulp material. 3. The method of claim 2, wherein the optical brighteners are selected from dilsulfonate, tetrasulfonate or hexasulfonate stilbene derivatives. The method of claim 1, further comprising contacting the bleached pulp material with one or more polycarboxylates. 12. The method of claim 11, wherein said polycarboxylate is partially neutralized polyacrylic acid. The method of claim 1, further comprising contacting the bleached pulp material with one or more optical brighteners, one or more chelating compounds, and one or more polycarboxylates. 3. The method of claim 2, wherein the reducing agents and optical brighteners are mixed in a surface sizing solution and applied to the bleached pulp material in a size press. Reducing the whiteness of the bleached pulp material during storage, comprising adding an effective amount of one or more reducing agents and optionally one or more chelating compounds, one or more polycarboxylates, or combinations thereof to the bleached pulp material And how to prevent sulfidation. 16. The whiteness reduction of bleached pulp material according to claim 15, wherein the reducing agents and optional chelate compounds and polycarboxylates are added to the bleached pulp after the bleaching step in the storage, mixing or conveying chest. And how to prevent sulfidation. Bleached pulp material prepared by the method according to claim 1 and having increased whiteness and increased resistance to thermal sulfiding. Iii) providing bleached pulp; Ii) forming an aqueous stock suspension comprising said bleached pulp; Iii) draining said stock suspension and forming a sheet; And Iii) drying the sheet; Wherein an effective amount of one or more reducing agents is added on the bleached pulp, the stock suspension or the sheet, wherein the paper product has increased whiteness and resistance to thermal sulfiding. 19. The paper product of claim 18 further comprising, on the bleached pulp, the stock suspension or the sheet, a paper product which adds one or more chelating compounds, one or more optical brightening agents or one or more polycarboxylates or combinations thereof. How to manufacture. A paper product made according to the method of claim 18. A bleached pulp material comprising a blended product of bleached pulp and an effective amount of reducing agent and having a higher whiteness and increased resistance to sulfidation when compared to similar pulp materials without the reducing agent. The bleached pulp material of claim 21 further comprising an effective amount of one or more chelating compounds, optical brightening agents or polycarboxylates or combinations thereof. A formulation comprising one or more reducing agents, one or more chelate compounds or one or more polycarboxylic acids. A formulation comprising one or more reducing agents and one or more optical brighteners and optionally one or more chelating compounds, one or more polycarboxylates, or combinations thereof.