JP2008536020A - Improved composition and process for papermaking - Google Patents

Abstract

Compositions and processes have been identified that, when applied between the various steps of the papermaking process, maintain and enhance the whiteness of the pulp or paper material and improve the color. When used in combination with optical brighteners and / or chelating agents, the agents exhibit synergistic effects not previously found in the paper process.
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Description

  The present invention relates to compositions and processes that improve whiteness and fluorescence properties in pulp and paper making to prevent loss of whiteness and increase resistance to yellowing by heat. More specifically, the present invention relates to a composition that effectively enhances the whiteness and fluorescent properties of a paper product and increases its thermal stability, alone or in the presence of a fluorescent whitening substance. .

BACKGROUND OF THE INVENTION Pulp made by mechanical or chemical pulping processes possesses a color that can range from dark brown to milky white depending on the type of wood used and the fiber dissociation process. The pulp is bleached to produce a blank product for many applications.

  Bleaching is the removal or alteration of light absorbing material found in unbleached pulp. The purpose in mechanical pulp bleaching is to decolorize the pulp without solubilizing the lignin. Usually, either reducing (eg, sodium hyposulfite) or oxidizing (eg, hydrogen peroxide) bleaching agents are used. Bleaching is often a multi-step process. Chemical pulp bleaching is an extension of delignification that begins in the cooking step. Bleaching is often a multi-step process, and each step can include chlorine dioxide bleaching, oxygen / alkaline delignification, and peroxide bleaching.

  Discoloration primarily due to thermal degradation results in yellowing and loss of whiteness in the resulting paper product at various steps in the papermaking process employing bleached pulp. There is considerable effort in the industry for chemicals such as bleaches and brighteners that improve the fluorescent properties of the finished paper or paper product. To date, however, the results are far from satisfactory and the economic loss due to discoloration and yellowing is still a considerable problem in the industry today. Accordingly, there remains a need for suitable and practical solutions to the loss of whiteness and adverse yellowing of pulp and paper.

SUMMARY OF THE INVENTION The present invention provides compositions and methods that improve and stabilize whiteness in a papermaking process and increase resistance to yellowing.

  In one embodiment, the present invention comprises: (1) providing a bleached pulp material; (2) contacting the bleached pulp material with an effective amount of one or more reducing agents; A process for preparing a bleached pulp material having enhanced whiteness and enhanced resistance to yellowing by heat.

  In another aspect, the present invention comprises: (1) preparing bleached pulp; (2) forming a raw aqueous suspension containing the bleached pulp; and (3) draining the raw suspension. And (4) drying the sheet; and one or more effective amounts for the bleached pulp or the raw material suspension or on the sheet. Is a method for producing a paper product having enhanced whiteness with added reducing agent and enhanced resistance to yellowing by heat.

  In another aspect, the present invention is a method for preventing loss of whiteness and yellowing of a bleached pulp material during storage comprising an effective amount of one or more reducing agents, and optionally one type. Or adding one or more chelating agents, or one or more polycarboxylates to the bleached pulp material.

  In another aspect, the present invention is a bleached pulp material comprising a blended product of bleached pulp and an effective amount of a reducing agent, wherein the bleached pulp material is not treated with the reducing agent. And a bleached pulp material having greater whiteness and increased resistance to yellowing when compared.

  Applicants also note that reducing agents combined with chelating agents effectively enhance the whiteness of paper products, and further, reducing agents used in combination with fluorescent whitening agents are said fluorescent whitening agents. It has also been found that the color system can be improved while improving the effect of. Thus, in an additional aspect, the present invention uses a reducing agent in combination with a chelating agent and / or a fluorescent brightening agent to provide greater whiteness and enhanced resistance to yellowing due to heat. And a bleached pulp material having an improved color system.

  The reducing agent, the fluorescent brightening agent, and the chelating agent can be used alone or in combination with known additives to enhance the quality of a desired paper product.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved process for producing paper and paper products that exhibit high fluorescent whiteness. Prepared from bleached pulp and bleached pulp by adding one or more reducing agents as defined herein to pulp, paper, board or thin paper at any point in the papermaking process Stabilization of whiteness, improvement of color and enhancement of whiteness against yellowing due to heat of the resulting paper product can be achieved.

  Whiteness is the whiteness of pulp or paper on a scale ranging from 0% (absolute black) due to reflection from the paper to blue light (457 nm) to 100% (relative to the MgO standard having an absolute whiteness of about 96%). Is a term used to describe “Loss of whiteness due to heat” is the loss of whiteness of paper and pulp under the influence of time, temperature and humidity (non-photochemical whiteness loss). “Loss of whiteness during storage” is the loss of whiteness due to heat over time under storage conditions.

  Yellowing (whiteness reversal) of bleached pulp material is the loss of whiteness over time of bleached pulp and paper, board, thin paper and related materials prepared from bleached pulp.

  The reducing agents described herein are suitable for use in any bleached pulp material used in a papermaking process and any paper product prepared from bleached pulp. As used herein, “bleached pulp material” means bleached pulp and paper products such as paper, paperboard, and thin paper prepared from bleached pulp.

  Examples of the reducing agent according to the present invention include chemical substances that can convert a functional group in bleached pulp from a high oxidation species to a low oxidation species. Advantages from this conversion include whiteness stability in papermaking machines and enhanced performance of fluorescent brighteners.

  In one embodiment, the reducing agent includes sulfite, bisulfite, metabisulfite (pyrosulfite), sulfoxylate, thiosulfate, dithionite (hydrosulfite), polythionate, form. Amidine sulfinic acid and salts and derivatives thereof, formaldehyde bisulfite addition products and other aldehyde bisulfite addition products, sulfinamide and ether of sulfinic acid, sulfenamide and ether of sulfenic acid, sulfamide, phosphine, phosphonium Selected from the group consisting of salts, phosphites, and thiophosphites.

As used herein, “sulfite” refers to sulfite H ₂ SO ₃ such as dibasic alkali and alkaline earth metal salts such as sodium sulfite (Na ₂ SO ₃ ) and calcium sulfite (CaSO ₃ ). Of the dibasic metal salt.

“Bisulfite” is a monobasic salt of sulfite H ₂ SO ₃ such as monobasic salts of alkali and alkaline earth metals such as sodium hydrogen sulfite (NaHSO ₃ ), magnesium hydrogen sulfite (Mg (HSO ₃ ) ₂ ). Means a metal salt.

“Sulfoxylate” means a salt of sulfoxylic acid H ₂ SO ₂ such as zinc sulfoxylate (ZnSO ₂ ).

“Metabisulfite (pyrosulfite)” means a salt of pyrosulfite H ₂ S ₂ O ₅ such as sodium metabisulfite (Na ₂ S ₂ O ₅ ).

“Thiosulfate” means a salt of thiosulfite H ₂ S ₂ O ₃ such as potassium thiosulfate (Na ₂ S ₂ O ₃ ).

"Polythionate" is sodium trithiones acid _{(Na 2 S 3 O 6)} , and, such as salts of dithionite _H 2 _S 2 _{O 6,} such as sodium dithionite _Na 2 _S 2 _{O 6,} polythionic acid _H 2 S _It means a salt of _n O ₆ (n = 2 to 6).

“Dithionite (hydrosulfite)” is dithionite (hydrosulfite) such as sodium dithionite (hydrosulfite) (Na ₂ S ₂ O ₄ ), magnesium dithionite (MgS ₂ O ₄ ), and the like. Hyposulfite) means a salt of H ₂ S ₂ O ₄ .

“Formamidine sulfinic acid (FAS)” means compounds of the formula H ₂ NC (═NH) SO ₂ H and salts and derivatives of the compounds such as the sodium salt H ₂ NC (═NH) SO ₂ Na .

"Aldehyde bisulfite addition product", R ₁ is alkyl, alkenyl, as selected from aryl, and arylalkyl, refers to a compound of formula _{R 1 CH (OH) SO 3} H and their metal salts. Representative aldehyde bisulfite addition products include formaldehyde bisulfite addition products HOCH ₂ SO ₃ Na and the like.

“Sulfinamide and ether of sulfinic acid” means a compound of formula R ₁ —S (═O) —R ₂ , wherein R ₁ is defined herein and R ₂ is OR ₃ and NR ₄ R ₅ is selected from: wherein, R ₃ to R ₅ are independently alkyl, alkenyl, aryl and arylalkyl. Representative sulfinamides include ethylsulfin dimethylamide (CH ₃ CH ₂ S (═O) N (CH ₃ ) ₂ ) and the like.

“Sulfenamide and ether of sulfenic acid” means a compound of formula R ₁ —S—R ₂ , wherein R ₁ and R ₂ are defined above. Representative sulfenamides include ethylsulfen dimethylamide (CH ₃ CH ₂ SN (CH ₃ ) ₂ ) and the like.

“Sulfamide” means a compound 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.

“Phosphine” means a derivative of phosphine PH ₃ , which is a common organic substituted phosphine of formula R ₆ R ₇ R ₈ P, where R ₆ -R ₈ are independently H, alkyl, alkenyl, aryl , Arylalkyl and NR ₄ R ₅ , wherein R ₄ and R ₅ are defined above. Representative examples of phosphine include (HOCH ₂ ) ₃ P (THP).

“Phosphite” is a derivative of phosphorous acid P (OH) ₃ such as an organic substituted phosphite of formula (R ₃ O) (R ₄ O) (R ₅ O) P, R _{3 to} R ₅ are defined above. A typical phosphite includes (CH ₃ CH ₂ O) ₃ P.

“Thiophosphite” means a derivative of phosphorothioic acid HSP (OH) ₂ such as an organic substituted thiophosphite of formula (R ₃ O) (R ₄ O) (R ₅ S) P R _{3 to} R ₅ are defined above. Representative thiophosphites include (CH ₃ CH ₂ O) ₂ (CH ₃ CH ₂ S) P.

“Phosphonium salt” means an organic substituted phosphine of formula R ₁ R ₃ R ₄ R ₅ P ⁺ X ^— , where R ₁ and R _{4 to} R ₅ are defined above and X is any organic or Inorganic anion. Typical phosphonium salts include (HO ₂ CCH ₂ CH ₂ ) ₃ P ⁺ HCl ⁻ (THP), [(HOCH ₂ ) ₄ P ⁺ ] ₂ (SO ₄ ) ^{2 −} (BTHP), and the like.

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

  “Alkoxy” means an alkyl group attached to the parent molecular moiety through an oxygen atom. Representative alkoxy groups include methoxy, ethoxy, propoxy, butoxy and the like. Methoxy and ethoxy are preferred.

  “Alkyl” means a monovalent group derived from a straight or branched saturated hydrocarbon by the removal of a single hydrogen atom. Alkyl can be unsubstituted or 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.

  “Alkylene” means a divalent group derived from a straight or branched saturated hydrocarbon by removal of two hydrogen atoms, for example, 1,2-ethylene, 1,1-ethylene, 1,3 -Propylene, 2,2-dimethylpropylene and the like.

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

  “Aryl” means aromatic carbocyclic and heterocyclic radicals having about 5 to about 14 ring atoms. Aryl can be unsubstituted or substituted with one or more groups selected from amino, alkoxy, hydroxy and halogen. Representative aryls include phenyl, naphthyl, phenanthryl, anthracyl, pyridyl, furyl, pyrrolyl, quinolyl, thienyl, thiazolyl, pyrimidyl, indolyl and the like.

  “Arylalkyl” means an aryl group attached to the parent molecular moiety through an alkylene group. 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, sulfoxylate, metabisulfite, thiosulfate, polythionate, hydrosulfite, formamidine sulfinate.

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

  In one embodiment, the reducing agent is sodium bisulfite.

  The process of the present invention can be carried out in conventional papermaking equipment. Although papermaking equipment varies in operation and mechanical design aspects, the process by which paper stock is produced in various equipment includes common steps. Papermaking typically includes a pulping step, a bleaching step, a raw material preparation step, a wet end step and a dry end step.

  In the pulping step, individual cellulose fibers are liberated from the source of cellulose by mechanical or chemical action, or both. Representative sources of cellulose include, but are not limited to, wood and similar “woody” plants, soy, rice, cotton, wheat straw, flax, manila hemp, hemp, bagasse, lignin-containing plants, and raw paper and recycled Examples include used paper, thin paper, and paperboard. Such pulps include, but are not limited to, groundwood pulp (GWD), bleached groundwood pulp, thermomechanical pulp (TMP), bleached thermomechanical pulp, chemical thermomechanical pulp (CTMP), bleached chemical thermomechanical pulp, Deinked pulp, kraft pulp, bleached kraft pulp, sulfite pulp, and bleached sulfite pulp. Although recycled pulp may or may not be bleached in the recycling step, it is assumed that they are inherently bleached. Any of the aforementioned pulps that have not been previously bleached may be bleached as described herein to provide a bleached pulp material.

  In one embodiment, the bleached pulp material is made from virgin pulp, recycled pulp, kraft, sulfite pulp, mechanical pulp, any combination of such pulp, recycled paper, thin paper, and the listed such pulp. Selected from the group consisting of any paper material or combinations thereof.

  A further advantage of the present invention is that, according to the present invention, low cost mechanical pulp can be substituted for high cost kraft in print grade kraft machine paper. The use of the chemistry and methods described herein increases the whiteness and stability against yellowing and allows the use of larger amounts of mechanical pulp, resulting in the resulting paper product Correspondingly, costs are reduced without loss of quality.

  The pulp is suspended in water in the raw material preparation step. In this step, whitening agents, dyes, pigments, fillers, antibacterial agents, antifoaming agents, pH control agents, and drainage aids can also be added to the raw materials. As used in this disclosure, “raw material preparation” includes operations such as dilution, screening and washing of the raw material suspension that can be performed prior to web formation.

  The wet finishing step of the papermaking process consists of depositing a raw material suspension, i.e., pulp slurry, on a wire mesh or mesh of a papermaking machine to form a continuous web of fibers, draining the web and consolidating the web, Forming a sheet. Any paper machine known in the art is suitable for use with the process of the present invention. Examples of such machines include a circular net paper machine, a long net paper machine, a twin wire forming machine, a tissue paper machine, and the like, and improvements thereof.

  In the dry end step of the papermaking process, the web is dried and can be subjected to additional processing such as size pressing, calendering, spraying with surface modifiers, printing, cutting, corrugation and the like. In addition to the size press and calendering water box, the dried paper material can be sprayed using a spray boom.

  Applicants have also noted that reducing agents combined with chelating agents, as described below, effectively improve the whiteness of paper products by increasing the thermal stability of the pulp and reducing the colored structure in the pulp. Found to improve.

  In one embodiment, one or more chelating agents are added to the bleached pulp or paper product. Suitable chelating agents according to this example include compounds that chelate transition metals that form colored products with pulp components and that catalyze color-forming reactions in bleached pulp or paper products Is mentioned.

  In one embodiment, the chelating agent is a compound selected from the group consisting of organic phosphonates, phosphates, carboxylic acids, dithiocarbamates, any salt of the preceding member, and any combination thereof. It is.

“Organic phosphonates” include HEDP (CH ₃ C (OH) (P (O) (OH) ₂ ), 1-hydroxy-1,3-propanediylbis-phosphonic acid ((HO) ₂ P (O)). Phosphonic acid HP (O) (OH) ₂ containing a single C—P bond, such as CH (OH) CH ₂ CH ₂ P (O) (OH) ₂ )), preferably 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 _{P (O) (OH) 2} ) 2), HEBMP (N (CH 2 P (O) (OH) 2) 2 CH 2 CH 2 OH) adjacent to the C-P bond as such (in the vicinity) An organic derivative of phosphonic acid HP (O) (OH) ₂ containing a single C—N bond.

“Organic phosphates” are phosphonic acid P (s) containing a single C—P bond, such as triethanolamine tri (phosphate ester) (N (CH ₂ CH ₂ OP (O) (OH) ₂ ) ₃ ). O) means an organic derivative of (OH) ₃ .

“Carboxylic acid” is an organic compound containing one or more carboxy groups —C (O) OH, preferably 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 alkali and alkaline earth metal salts thereof, etc. Means an aminocarboxylic acid containing a single C—N bond adjacent to (in the vicinity of) the C—CO ₂ H bond.

  “Dithiocarbamate” includes monomeric dithiocarbamate, polymeric dithiocarbamate, polydiallylamine dithiocarbamate, 2,4,6-trimercapto-1,3,5-triazine, disodium ethylenebisdithiocarbamate And disodium dimethyldithiocarbamate.

  In one embodiment, the chelating agent is a phosphonate.

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

  In one embodiment, the chelating agent is a carboxylic acid.

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

  Applicants have also found that the use of a reducing agent in combination with an optical brightener (“OBA”) enhances the effect of the optical brightener (OBA). The reducing agent also improves the color system. This can reduce the amount of brighteners such as OBA and blue dyes required to achieve comparable whiteness and color. Replacing some of the OBA and dyes with reducing agents allows pulp and paper manufacturers to reduce manufacturing costs while maintaining acceptable levels of whiteness in paper products and achieving target colors And the total amount of OBA and dye present can be reduced. In certain cases, it may be possible to completely eliminate the dye and maintain the color.

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

  "Fluorescent whitening agent" is a fluorescent dye or pigment that absorbs ultraviolet light when added to the raw material and shines white by re-releasing it at a high frequency (blue) in the visible spectrum. A fluorescent dye or pigment that provides an appearance to a paper sheet. Representative optical brighteners include, but are not limited to, azoles, biphenyls, coumarins; furans; Ecobrite® and Eccowhite® available from Eastern Color and Chemicals, Rhode Island Ionic brighteners such as anionic, cationic, and anionic (neutral) compounds such as compounds; naphthylimides; pyrazines; Leucophor® available from Clariant (Muttens, Switzerland) ) Grade optical brighteners and substituted stilbenes such as Tinopal® from Ciba Specialty Chemicals (Basel, Switzerland); for example, but not limited to, such brighteners Alkali metal salts, alkaline earth metal salts, transition metal salts, organic salts and Salts of such compounds such as ammonium salts; and, as combinations of one or or more of the above materials.

  In one example, the optical brightener is selected from the group of disulfonated, tetrasulfonated and hexasulfonated Tinopal® OBA.

  The amount of reducing agent, chelating agent and / or optical brightener added is necessary to achieve the desired whiteness and yellowing resistance of the bleached pulp or paper products prepared from the bleached pulp. And can be readily determined by those skilled in the art based on the properties of the chelator or optical brightener, 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 whiteness of the pulp or paper and the resistance to yellowing by heat compared to pulp or paper not treated with the reducing agent. This is the amount of reducing agent that is enhanced. Methods for determining whiteness and resistance to yellowing by heat are described herein.

  Typically, for bleached pulp or paper products, from about 0.005 to about 2% by weight, preferably from about 0.05 to about 0.25% by weight, based on oven dried pulp Of reducing agent is added.

  In typical applications, the bleached pulp or paper product is about 0.001 to about 1% by weight, preferably about 0.01 to about 0.1% by weight, based on the oven-dried pulp. % Phosphonate, phosphate or carboxylic acid chelator and / or about 0.002 to about 0.02 wt% dithiocarbamate chelator.

  The optical brightener is typically added in an amount of about 0.005 to about 2 wt.%, Preferably 0.05 to about 1 wt.%, Based on the oven-dried pulp. .

  The reducing agent, chelating agent, and / or fluorescent whitening agent can be added to the bleached pulp or paper material at any point in the paper or thin paper manufacturing process. Typical addition locations include, but are not limited to: (a) in a stand-by container, for pulp slurry; (b) in a storage, blending or transfer container for bleaching steps. Later on the pulp; (c) After the bleaching, washing and dewatering followed by cylinder or flash drying; against the pulp; (d) Before or after the cleaner; (e) A fan pump for the paper machine headbox Before or after; (f) against the white water of the papermaking machine; (g) against a silo or spill receiver; (h) in the press section using, for example, a size press, applicator or spray bar; (i) For example, in a drying section using a size press, applicator or spray bar; (j) on a calendar using a wafer container; and / or (k) in an off-machine applicator or size press. On paper material Te; and / or, in the (l) bending control unit.

  The exact location where the reducing agent, chelating agent and / or optical brightener should be added depends on the particular equipment involved, the exact process conditions being used, and the like. In certain cases, reducing agents, chelating agents, and / or optical brighteners may be added at one or more locations for optimal effectiveness.

  Application can be any means conventionally used in the papermaking process, such as by “split feed”, but according to such feed, a portion of the reducing agent, chelating agent, and / or fluorescent whitening agent. Is applied at one point in the papermaking process, such as on a pulp or wet sheet (before the dryer), and the remaining portion is added at a subsequent point, such as a size press.

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

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

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

  In these various locations, reducing agents, chelating agents and / or optical brighteners can also be used to improve yields, sizing aids and solutions, starch, precipitated calcium carbonate, ground calcium carbonate, or other clays or It can be added with fillers and carriers or additives typically used in papermaking, such as whitening additives.

In one embodiment, the reducing agent, chelating agent and / or optical brightener is one or more partially neutralized polycarboxylic acids, preferably n is from about 10 to about 50,000. Used in combination with a polycarboxylic acid such as polyacrylic acid (CH ₃ CH (CO ₂ H) [CH ₂ CH (CO ₂ H)] _n CH ₂ CH ₂ CO ₂ H. Can be neutralized to a target pH with an alkali such as sodium oxide (typically 5-6 as discussed below).

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

  In one embodiment, the present invention includes one or more reducing agents and one or more fluorescent brighteners, and optionally one or more chelating agents, or one or more. A preparation comprising a polycarboxylate of The preparation according to this example preferably has a pH of about 7-11, more preferably about 9-10.

  The above reducing agents, chelating agents, optical brighteners and polycarboxylates are used in addition to other additives conventionally used in papermaking to provide one or more types of finished paper products Can be improved, assist the manufacturing process of the paper itself, or both. These additives are generally characterized as either functional additives or control additives.

  Functional additives are typically additives used to enhance or impart certain particularly desired properties to the finished paper product, including but not limited to brighteners, dyes, fillers, Examples include sizing agents, starches and adhesives.

  Control additives, on the other hand, are additives that are incorporated during the process of manufacturing the paper material to improve the overall process without significantly affecting the physical properties of the paper material. Control additives include biocides, yield improvers, antifoam agents, pH control agents, pitch control agents, and drainage aids. Paper materials and paper products made using the process of the present invention may contain one or more functional and / or control additives.

  Pigments and dyes add color to the paper material. As dyes, organic compounds having a conjugated double bond system; azo compounds; metal azo compounds; anthraquinones; triaryl compounds such as triarylmethane; quinoline and related compounds; acid dyes (along with organic cations such as alum) Anionic organic dyes containing sulfonic acid groups used); basic dyes (cationic organic dyes containing amine functional groups); and direct dyes (high molecular weight and specific direct to cellulose) Acid-type dyes having affinity); and combinations of suitable dye compounds listed above. Pigments are finely divided inorganic compounds that can be either white or colored. The most commonly used pigments in the paper industry are clay, calcium carbonate and titanium dioxide.

The filler is added to the paper material to increase milkiness and whiteness. Fillers include, but are not limited to, calcium carbonate (calcite); precipitated calcium carbonate (PCC); calcium sulfate (including various hydrated forms); calcium aluminate; zinc oxide; magnesium silicate such as talc; Titanium dioxide (TiO ₂ ), such as pyrite or goldstone; clay or kaolin composed of hydrated SiO ₂ and Al ₂ O ₃ ; synthetic clay; mica; meteorite; inorganic aggregate; pearlite; sand; gravel Sandstone; glass beads; aerogel; xerogel; seagel; fly ash; alumina; microspheres; hollow glass spheres; porous ceramic spheres; cork; seeds; lightweight polymer; Pumice; exfoliated rock; waste concrete product; hydraulic cement particles partially or non-hydrated And, diatomaceous earth, as well as combinations of such compounds.

The sizing agent is added to the paper material during the manufacturing process, thereby helping to develop resistance to the liquid that penetrates the paper material. The sizing agent can be an internal sizing agent or an external (surface) sizing agent and can be used for hard sizing or relaxation sizing or both sizing methods. More specifically, the sizing agent includes: rosin; rosin precipitated with alum (Al ₂ (SO ₄ ) ₃ ); abietic acid and abietic acid analogs such as neoabietic acid and levopimaric acid; Stearic acid derivatives; ammonium zirconium carbonate; silicones and silicone-containing compounds such as RE-29 available from GE-OSI and SM-8715 available from Dow Corning (Midland, MI); R, such as Gortex Fluorine compounds of general formula CF ₃ (CF ₂ ) _n R as anionic, cationic or another functional group; Aquapel 364, all commercially available from Hercules (Wilmington, Delaware) Aquapel (I 752, Her on) 70, Hercon 79, Precise 787, Precise 2000 and Precise 3000, alkyl ketene dimers (AKD); and alkyl succinic anhydride (ASA); ASA or AKD and cationic starch emulsions ASA with starch alum; starch; hydroxymethyl starch; carboxymethyl cellulose (CMC); polyvinyl alcohol; methyl cellulose; alginate; waxy substance; waxy substance emulsion; and a combination of such sizing agents. Can be mentioned.

  Starch has many uses in papermaking. For example, it functions as a retention agent, dry strength agent and surface sizing agent. Starches include, but are not limited to, various amounts of amylose and amylopectin, such as amylose; amylopectin; 25% amylose and 75% amylopectin (corn starch) and 20% amylose and 80% amylopectin (potato starch). Hydrolyzed starch; Heated starch, also known in the art as "pasted starch"; such as resulting from the reaction of tertiary amines with starch to form quaternary ammonium salts Cationic starch; anionic starch; amphoteric starch (including both cationic and anionic functionality); cellulose and cellulose derived compounds; and combinations of these compounds.

  The method of the present invention yields a paper product having a white surface. Furthermore, the novel composition described above protects the paper material from long-term discoloration during normal use.

  The foregoing can be better understood with reference to the following examples, which are presented for illustrative purposes and are not intended to limit the scope of the invention.

Experimental example

  In these experimental examples, adequate pH for the agent or composition being tested was achieved by the addition of sufficient 50% aqueous sodium hydroxide. All percentages in these experimental examples are given in weight percent based on dry pulp.

In these experimental examples, the following phrases shall have the meanings indicated:
Br is ISO brightness R457 (TAPPI 525);
Ye is E313 yellowness;
ImBr is R457 whiteness after application;
TABr is R457 whiteness after thermal degradation;
TA loss is the loss of whiteness after thermal degradation;
Inh. Is% inhibition of whiteness loss;
% Inh. = 100-100 x (ImBr-TABr) / (ImBr-TABr) _control ;
WI is E313 whiteness;
TMP is a thermomechanical pulp;
CTMP is a chemical thermomechanical pulp;
RMP is a refined mechanical pulp;
OBA is an optical brightener;
FAS is formamidine sulfinic acid;
TCP _{is, (HOCH 2 CH 2) 3} PHCl, i.e. tris- carboxyethyl phosphonium hydrogen chloride;
BTHP is [(HOCH ₂ ) ₄ P] ₂ (SO ₄ ), ie, tetrahydroxymethylphosphonium sulfate;
THP is, (HOCH _{2) 3} P, i.e. tris- hydroxymethyl phosphine;
EDTA is (HO ₂ CCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CO ₂ H) ₂ , ie ethylenediaminetetraacetic acid;
DTPA is (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 , ie diethylenetriaminepentaacetic acid;
DTMPA _{is, H 2 O 3 PCH 2 N} [CH 2 CH 2 N (CH 2 PO 3 H 2) 2] 2, i.e. diethylene - triamine - penta methylene phosphonic acid; and,
DTC is sodium dimethyldithiocarbamate.

Handmade paper is produced from the treated bleached pulp and used in the experiment, in which case the reducing agent is applied on the wet sheet before drum drying or after drum drying (before or after pressing) (drum Temperature during drying: 100 ° C.). The third option was split supply application. One or more surface sizing applications were applied on the drum dryer.

  The loading of the agent or composition solution tested was determined based on the dry weight of the pulp sample. The agent or composition solution was applied as uniformly as possible using a rod as an aqueous solution. Each test sheet was dried under a uniform condition using a laboratory drum dryer (once) and then subjected to an accelerated aging test as described below after measuring the whiteness.

Whiteness reversal experiment (thermal degradation, paper):
A 3 × 9 cm sample of the detached test sheet was maintained in a water bath at 70 ° C. and 100% humidity for about 3 days. Each sample was equilibrated in a humidity chamber before measuring the whiteness.

Whiteness reversal experiment (heat degradation, pulp):
Pulp samples (10% consistency once daily, 5 g pulp) were sealed in plastic bags and maintained at 70 ° C. for 3-6 hours in a water bath. Handmade paper was prepared and equilibrated in a humidity chamber before measuring the whiteness.

Test 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 measurement.
Trace pipette.
Surface sizing application kit (pad, sizing agent, 3 application rods).
Constant humidity chamber (23 ° C., 50% humidity).
A water bath / thermostat containing a floating plastic box with a 100 mL paper sample applied cuvette for the dipping method.

Dry surface application procedure (surface sizing):
1. Prepare 8 × 8 inch handsheets according to standard procedures. The target dry weight is 2.5 g. Pass the wet handmade paper through a drum dryer for one cycle.
2. Cut the sheet into four smaller rectangles (each weighing about 0.625 g).
3. Using a scotch tape that is longer than the side of the sheet, tape one side of the small rectangle (test sheet) to the glass pad.
4). The application rod is placed on the scotch tape and a 0.2 ml volume of the mixture is applied onto the tape against the rod using a micropipette.
5. The agent solution is applied in such a way that it is evenly distributed on the tape and covers the entire test sheet.
6). The solution is quickly applied to the sheet from the tape using the rod so that the reducing agent compound solution is uniformly applied over the entire sheet.
7). The test sheet is drum dried and allowed to equilibrate at room temperature.
8). Measure whiteness and yellowness.

Dry surface application procedure (surface sizing, dipping method):
1. Prepare 8 × 8 inch handsheets according to standard procedures. The target dry weight is 2.5 g. Pass the wet handmade paper through a drum dryer for one cycle.
2. Cut 1/8 strip of sheet (0.31 g).
3. Prepare a solution of pre-cooked starch and reducing agent composition solution (if necessary) in a 50 ml test tube based on the predetermined pick-up ratio and target addition amount.
4). A paper strip is dipped in the above solution for 10 seconds, dropped for 35 seconds and then passed through a press.
5. The test sheet is drum dried and allowed to equilibrate at room temperature.
6). Measure whiteness and yellowness.

Wet end application procedure:
A 1.8 × 8 inch sheet is produced and dewatered using a press with two blotter papers at the bottom and one blotter paper at the top. The consistency of the pressed sheet is about 40%.
2. The top blotter and the bottom blotter are removed from the sheet after pressing.
3. Cut the sheet together with one blotter paper at the bottom into 4 smaller test sheets of equal dimensions (the approximate dry weight of the sheet is 0.625 g).
4). The test sheet is taped to a glass pad with blotting paper 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 wet blotter paper, the tape is removed, and the blotter paper is separated from the test sheet. The blotter paper is discarded.
7). The test sheet is then drum dried and equilibrated at room temperature.

Split supply application procedure:
1. According to standard procedures, 8 × 8 inch sheets are produced.
2. Four blotting papers are applied to the sheet formed on the screen.
3. Next, the sheet together with blotting paper is pressed using a heavy metal roller. This process removes excess moisture from the sheet and increases the consistency of the sheet to about 20%.
4. Three top blotters are removed from the sheet.
5. Next, the sheet and a piece of blotter paper are removed from the screen and cut into four smaller pieces as described in the “Wet End Application Procedure”.
6). The sheet and blotter paper are then taped to the glass pad as described in “Wet End Application Procedure”.
7). Apply Solution 2 as described in “Wet End Application Procedure”.
8). The test sheet is then pressed with two blotters on each side.
9. After pressing, remove all blotter paper and drum dry the sheet. Next, solution 2 is applied to the sheet and measured as described in steps 3 to 8 of the “Dry Surface Application Procedure”.

Pulp application procedure:
Each chemical was added directly to the pulp (dilute raw material or thick raw material) and mixed with the pulp in a sealed bag. In the pulp application procedure for OBA enhancement, each chemical was added directly to the bleached kraft pulp at 20% consistency, mixed with the pulp in a sealed bag and maintained at 45-80 ° C for 30 minutes. The pulp was diluted to 5% consistency, OBA was added, mixed with the pulp, and the slurry was maintained at 50 ° C. for 20 minutes. The slurry was then further diluted and handsheets were prepared according to standard procedures.

  Test results.

1. Crusher trial data was collected on a Southern Craft Mill. The following table gives sample data. In some tests, applying the product (Composition A) in a size press with OBA in sizing solution at 5 lb / ton and further additions (reflected in the decrease in DE value) A 1.5 point whiteness increase was consistently achieved with the improved color of the sheet. Returning to standard mill conditions (no osmotic composition applied) resulted in the whiteness decreasing to the background level. This experiment was reproduced three times.

  Several compositions were tested and gave good results in laboratory simulations for PM applications. Each chemical (composition) not listed in Table 1 was applied as a 40% solution.

2. Reducing agent: Sodium metabisulfite (30% solution)

  Tables 3 to 8 illustrate the effect of sodium metabisulfite (metabisulfite), a reducing agent on paper whiteness, and the whiteness enhancing composition; the reducing agent partially reduces whiteness loss in the dryer. (Table 8) and whiteness is improved (Table 3 to Table 8). The chemistry further improves whiteness in the presence of OBA (Table 5).

3. Application in model surface size solution with reducing agent starch other than sodium metabisulfite

  Tables 9 to 11 illustrate the effects of reducing chemicals such as FAS and phosphorus (III) compounds other than sodium metabisulfite.

4). Chelating agent-metabisulfite composition

  Tables 12 to 27 illustrate the application of the composition when the reducing agent is combined with a single type or multiple types of chelating agents. Different combinations can be compared (all are valid). Each preparation configuration improves the long-term whiteness stability of the paper material against thermal degradation (Tables 24 to 27). This group of data also illustrates OBA activation by each composition (Tables 12-14, Table 25). Applying the above preparation configuration can reduce the amount of fluorescent brightener added. Tables 16 and 17 illustrate the effect of the above preparation composition on fluorescence.

5. Wet-end application: Separate application of the composition in the pulp that leads to improved performance of OBA applied at a later time Pulp application procedure for subsequent OBA enhancement (80 ° C.)

  Tables 28-30 illustrate the activation of OBA through prior application of the composition.

6). Wet-end application: introduction of low addition amount of dithiocarbamate into the composition

  The above data (Tables 31 to 33) illustrate whiteness recovery and long-term stabilization upon application of the proposed preparation.

  Although the invention has been described above with reference to exemplary or exemplary embodiments, these embodiments are not intended to be exhaustive or limiting of the invention. On the contrary, the invention is intended to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.

Claims (24)

In a method of preparing a bleached pulp material having enhanced whiteness and enhanced resistance to yellowing by heat:
i) providing a bleached pulp material;
ii) contacting the bleached pulp material with an effective amount of one or more reducing agents;
A method characterized by comprising.   The method of claim 1, further comprising contacting the bleached pulp material with one or more optical brighteners.   2. The method of claim 1, further comprising contacting the bleached pulp material with one or more chelating agents.   The method of claim 1, wherein the bleached pulp material is virgin pulp, recycled pulp, kraft pulp, sulfite pulp, mechanical pulp, any combination of such pulp, recycled paper, thin paper, and so on. A method characterized in that it is selected from the group consisting of any paper material or paper product made from natural pulp, or a combination thereof.   2. The method according to claim 1, wherein the reducing agent is sulfite, bisulfite, metabisulfite (pyrosulfite), sulfoxylate, thiosulfate, dithionite (hydrosulfite), polythionic acid. Salts, formamidine sulfinic acid, and salts and derivatives thereof, formaldehyde bisulfite addition products and other aldehyde bisulfite addition products, sulfinamide and sulfinic acid ethers, sulfenamide and sulfenic acid ethers, sulfamides , A phosphine, a phosphonium salt, a phosphite, and a thiophosphite.   6. The method of claim 5, wherein the reducing agent is selected from the group consisting of substituted phosphines, sulfites, bisulfites, and metabisulfites.   7. A method according to claim 6, wherein the reducing agent is sodium bisulfite.   4. The method of claim 3, wherein the chelating agent is selected from the group consisting of organic phosphonates, phosphates, carboxylic acids, dithiocarbamates, any salt of the preceding member, and any combination thereof. A method characterized by being made.   9. The method of claim 8, wherein the chelating agent is diethylene-triamine-pentamethylenephosphonic acid (DTMPA) and salts thereof, diethylenetriaminepentaacetic acid (DTPA) and salts thereof, and ethylenediaminetetraacetic acid (EDTA) and salts thereof. A method characterized in that it is selected from the group consisting of:   3. The method according to claim 2, wherein the optical brightener is selected from disulfonated, tetrasulfonated or hexasulfonated stilbene derivatives.   The method of claim 1 further comprising contacting the bleached pulp material with one or more polycarboxylates.   12. A method according to claim 11, wherein the polycarboxylate is partially neutralized polyacrylic acid.   The method of claim 1 wherein the bleached pulp material is contacted with one or more optical brighteners, one or more chelating agents, and one or more polycarboxylates. A method further comprising:   The method of claim 2 wherein the reducing agent and the optical brightener are mixed with a surface size solution and applied to the bleached pulp material in a size press.   An effective amount of one or more reducing agents and, optionally, one or more chelating agents, one type in a method of preventing loss of whiteness and yellowing of a bleached pulp material during storage. A method comprising the step of adding one or more polycarboxylates or combinations thereof to the bleached pulp material.   16. The method of claim 15, wherein the reducing agent and optional chelating agent and polycarboxylate are added to the bleached pulp in a storage, mixing or transfer container after the bleaching step. And how to.   A bleached pulp material prepared according to the method of claim 1 and having enhanced whiteness and enhanced resistance to yellowing by heat. In a method of producing a paper product having enhanced whiteness and enhanced resistance to heat yellowing:
i) providing bleached pulp;
ii) forming a raw aqueous suspension solution comprising the bleached pulp;
iii) draining the raw material suspension to form a sheet;
iv) drying the sheet;
And an effective amount of one or more reducing agents is added to the bleached pulp or the raw material suspension or on the sheet.   19. The method of claim 18, wherein the one or more chelating agents, one or more fluorescent whitening materials, or on the bleached pulp or the raw material suspension or on the sheet, or The method further comprises the step of adding one or more polycarboxylates or combinations thereof.   A paper product prepared according to the method of claim 18.   In bleached pulp material comprising a blended product of bleached pulp and an effective amount of reducing agent, the whiteness of the bleached pulp material is greater when compared to similar pulp materials without the reducing agent. And bleached pulp material with increased resistance to yellowing.   The bleached pulp material according to claim 21, further comprising an effective amount of one or more chelating agents, fluorescent whitening substances or polycarboxylates or combinations thereof. .   A preparation characterized in that it comprises one or more reducing agents, one or more chelating agents and one or more polycarboxylic acids.   In the preparation, one or more reducing agents, and one or more optical brighteners, and optionally one or more chelating agents, one or more polycarboxylates. Or a preparation comprising a combination thereof.