JP3998638B2 - Paper sizing method and sizing composition - Google Patents

Description

The present invention includes adding an aqueous composition comprising an agglomerate comprising a sizing agent to a cellulose suspension, whereby the composition mixes an aqueous solution of an aggregating agent and an aqueous dispersion comprising a sizing agent in any order. And the composition has a zeta potential of less than 20 mV. The present invention also includes an aqueous sizing composition.

In order to obtain paper suitable for printing and other commercial applications, different types of chemicals are added to the cellulosic suspension at the paper mill. One type of compound added can be used to make paper more resistant to the penetration of liquids such as aqueous solutions, commonly referred to as sizing agents. These sizing agents often contain a hydrophobic moiety, whereby the compound is only covalently bonded to or associated with the cellulose fibers. The performance of a sizing agent that is usually added to a suspension in the form of a dispersion or emulsion depends on many factors, such as the type of pipe in the suspension, i.e., chemical pulp, mechanical pulp, recycled fiber, retention aid. Other performance additives such as, and in particular, are affected by the amount of contaminants present in the suspension. Contaminants present in suspensions that have an effect on sizing agent yield are ionic compounds, especially ranging from salts to polymers with significant molecular weight. The presence of charged polymer compounds such as xylan in the suspension is often indicated by measuring the cation demand of the suspension. A higher cation requirement means a higher concentration of charged polymer compound in the suspension. Suspensions with high cation demand can be derived from the type of pulp used, ie recycled paper, the dilution water used, and the degree of circulation of white water in the paper mill. Paper mills in which white water is thoroughly circulated tend to end up with suspensions with high cation requirements. Therefore, one object of the present invention is to provide a paper sizing method, in which the paper is formed from a suspension containing cellulose fibers with high cation requirements and / or high conductivity. A further object is to improve the yield of the sizing agent, in particular the so-called first pass yield. The sizing composition of the present invention can be a fully sized paper without the need for additional addition of retention aids. Further objectives will be apparent below.

The sizing agent itself is a compound with hydrophobic characteristics, and therefore it is practically impossible to disperse / emulsify the sizing agent in an aqueous solution without the presence of a compound that affects or promotes the formation of the dispersion. . In addition, additional compounds may be required to stabilize the dispersion. The formation of a sizing dispersion prior to the addition of a sizing agent to the suspension is generally a prerequisite for obtaining a fully sized paper. Usually, the particle size or weight average particle size of the particles containing the sizing agent has an effect on sizing efficiency. Better sizing by convention is obtained when the particles containing the sizing agent are as small as possible, preferably 1 μm or less. However, it is an object of the present invention to provide a composition comprising an agglomerate comprising a sizing agent that is substantially larger than sizing particles in a normal dispersion. Surprisingly, the methods and compositions of the present invention are well sized without the use of retention aids, ie, papers having a Cobb value of 30 or less. In addition, the methods and compositions significantly improve sizing when applied to cellulose suspensions having high cation requirements and / or high conductivity. WO 00/34583 discloses a sizing dispersion that is stabilized by a cationic colloidal coacervate stabilizer, where the coacervate agent comprises an anionic component and a cationic component. The anionic and cationic components need to be present in a ratio such that the dispersion has a zeta potential of at least 20 mV, with a zeta potential of at least 40 mV being more preferred. The purpose of the coacervate is to stabilize the emulsified or dispersed sizing agent.

US Pat. No. 6,159,339 relates to a paper size consisting essentially of ASA / AKD and decomposed liquid cationic starch.

WO 9833979 relates to an aqueous dispersion comprising a cellulose reactive sizing agent comprising a low molecular weight cationic organic compound having a molecular weight of less than 10,000 and an anionic stabilizer.

The present invention relates to a paper sizing method and sizing composition described in the claims. More particularly, the present invention is a paper sizing method comprising preparing an aqueous suspension containing cellulose fibers, dehydrating said aqueous suspension, thereby forming a paper web, said method comprising cellulose Adding an aqueous composition comprising an agglomerate comprising a sizing agent to the suspension, wherein the composition comprises, prior to addition to the aqueous suspension, (i) an aqueous solution comprising at least one flocculant; and (Ii) The present invention relates to a paper sizing method which is obtained by mixing an aqueous dispersion containing a sizing agent in any order, and the composition has a zeta potential of less than 20 mV. In addition, the present invention also relates to an aqueous sizing composition as specified in the claims for an aqueous sizing composition comprising an agglomerate comprising a sizing agent, wherein the composition comprises (i) at least one agglomeration. Obtained by mixing in any order a solution containing the agent and (ii) an aqueous dispersion containing the sizing agent, the composition having a zeta potential of less than 20 mV.

According to a preferred embodiment of the present invention, the aqueous composition comprising agglomerates comprising a sizing agent is, prior to addition to the aqueous suspension, (i) an aqueous solution comprising at least one charged flocculant, and ( ii) obtained by mixing the charged aqueous dispersion containing the sizing agent in any order, whereby the charge of the flocculant is the opposite of the charge of the dispersion.

According to yet another preferred embodiment, the present invention is characterized in that a composition comprising an agglomerate containing a sizing agent is added to the suspension without adding one or more retention aids to the suspension. The present invention relates to a paper sizing method.

The solution flocculant is actually any compound or mixture of compounds, provided that the flocculant affects the flocculation / aggregation of the sizing particles when mixing the flocculant solution and the sizing agent dispersion. Also good. Preferably, the flocculant is selected from the group consisting of nonionic polymers, polyelectrolytes, surfactants, silica-based particles, inorganic aluminum-containing compounds, and mixtures thereof. If a charged flocculant is included in the aqueous solution, the aqueous sizing dispersion preferably has the opposite charge.

Examples of suitable nonionic polymers are polyalkylene oxides (also referred to as polyalkylene glycols), especially polyethylene oxide and phenolic resins. The phenolic resins chosen are phenols and aldehydes, preferably formaldehyde polycondensation products (commonly referred to as resoles and novolacs), and phenols modified with rosin acid from natural resins such as gum rosin, wood rosin and tall oil rosin. Resin. Usually, a mixture of a polyalkylene oxide and a phenol resin is used as a flocculant. Advantageously, the nonionic polymer is water soluble or water dispersible.

According to the above preferred embodiments, the present invention provides an aqueous solution wherein the aqueous composition comprises a charged aqueous dispersion or emulsion of a sizing agent (depending on the physical state of the sizing agent at ambient temperature), and a charged flocculant. (The charge of the flocculant is the opposite of the charge of the dispersion) and mixing the dispersion and solution, thereby obtaining an aqueous composition comprising an agglomerate comprising a sizing agent having a zeta potential of less than 20 mV. Relates to a paper sizing method and an aqueous sizing composition when produced by The term “charged aqueous dispersion” in the claims also means an aqueous emulsion charged depending on the type of sizing agent present in the dispersion. For example, if a sizing agent is present that is solid or nearly solid at ambient temperature, a dispersion is produced, but if the sizing agent is liquid at ambient temperature, an emulsion is obtained. The term “charged dispersion” refers to the overall charge of the dispersion / stabilization system of the dispersion. Therefore, if the charged flocculant of the solution is an anion (total anion), the dispersion containing the sizing agent should be a cation. On the other hand, if the charged flocculant is a cation (total cation), the dispersion should be an anion.

When referring to the solution's charged flocculant, its charge is either positive or negative depending on the charge of the dispersion. Therefore, the flocculant should not contain equal amounts of negative and positive charges. Thus, the charged flocculant is an anion or cation, i.e. the agent may have a total charge of an anion or cation, whereby the flocculant is only an anionic group, only a cationic group Or it can have both anionic and cationic groups, the latter being called amphoteric flocculants.

When producing an aqueous composition, the order in which the solution is mixed with the dispersion is not considered relevant. However, the solution containing the flocculant is preferably added to the aqueous dispersion. Any method of mixing the dispersion and solution may be applied, but it is preferred that the addition of the solution be adjusted so that the zeta potential of the resulting aqueous composition is less than about 20 mV during mixing, thereby Agglomerates comprising a sizing agent having a diameter substantially larger than normal sizing particles in the dispersion are obtained. Better flocculation of the sizing agent results in a zeta potential during mixing near the isoelectric point of the composition, for example, less than about 18 mV (ie, between -18 mV and +18 mV), more preferably less than about 15 mV (ie,- Between 5 mV and +5 mV).

According to the present invention, the zeta potential of the composition obtained after mixing should be less than about 20 mV. The term less than about 20 mV includes compositions having a zeta potential of less than 20 mV and greater than −20 mV. The zeta potential of the composition is preferably less than about 18 mV, more preferably less than about 15 mV, preferably less than about 10 mV or even less than 5 mV. The zeta potential of the composition after mixing may be further low as in the vicinity of the isoelectric point of the composition.

The charge of the aqueous composition, i.e. the dispersion / stabilization system, is usually ascertained by measuring the zeta potential. A positive value of the zeta potential indicates a cation dispersion, while a negative zeta potential indicates an anion dispersion. Zeta potential is described in the book “Introduction to Colloids and Surface Chemistry”, D. Measurements can be made using particle microelectrophoresis as described in Shaw, Butterworths.

Agglomerates comprising a sizing agent are agglomerates that are loosely packed with respect to the sizing agent when the sizing agent is evenly distributed within the agglomerates. Preferably, the agglomerates comprise from about 1% to about 40%, more preferably from about 3% to about 30%, most preferably from about 5% to about 20% sizing agent. The remainder of the agglomerate volume is believed to contain primarily water, and a small amount of aggregating agent and optionally a dispersing / stabilizing agent from the aqueous sizing dispersion. By convention, sizing particles in the micron range that are larger or considerably larger than sizing particles in the 1 micron range result in poor distribution of the sizing agent in the paper web, ultimately resulting in impaired sizing of the paper Bring. However, the agglomerates contained in the compositions of the present invention that have a sizing agent that is evenly distributed within the agglomerates can effectively spread the sizing agent at a reasonable dose of the composition on the fiber surface during the dry season. Estimated to give.

By mixing an aqueous solution containing a flocculant and an aqueous dispersion containing a sizing agent, flocculation of the sizing agent occurs, thereby causing at least about 5 μm, preferably at least about 10 μm, more preferably at least about 15 μm, optionally. A composition comprising agglomerates of sizing agent, preferably having a weight average diameter of at least about 22 μm is obtained. The upper limit weight average diameter of the agglomerates is significant depending on the process parameters, for example, the type of cellulose suspension and other performance chemicals added to the suspension, such as dry strength enhancers, wet strength enhancers, etc. Can change. For practical reasons, the weight average diameter of the aggregates is suitably 250 μm or less, preferably 100 μm or less, more preferably 80 μm or less. A preferred range for the weight average diameter of the agglomerates is from about 10 μm to about 100 μm, preferably from about 15 μm to about 60 μm, more preferably from about 22 μm to about 50 μm.

The weight average diameter of the agglomerates is measured using a Malvern Mastersizer Microplus (Malvern Instruments) with a small volume cell top. The weight average diameter in the claims represents a particle size distribution expressed as PSDD (v. 0.5), which represents a volume weighted particle size where 50% of the particles are below the indicated value. means.

The charged flocculant is preferably selected from the group consisting of polyelectrolytes, silica-based particles, inorganic aluminum-containing compounds, and mixtures thereof.

According to a preferred embodiment, the composition of the charged aqueous dispersion containing the sizing agent is not critical as long as the overall charge is a cation or an anion. The dispersion preferably includes a compound that promotes the formation of dispersed sizing particles and stabilizes the sizing particles. Such dispersing / stabilizing agents are preferably natural polymers such as polysaccharides such as cellulose derivatives and starches, and synthetic polymers such as vinyl addition polymers and condensation polymers. The particle size of the sizing agent in the dispersion may range from about 0.1 μm to about 2 μm. In addition, the charged aqueous dispersion may contain any of the agents referred to in this application as flocculants in addition to or in place of the stabilizing / dispersing agents. The type and amount of dispersion / stabilizer and / or flocculant in the dispersion is chosen so that the dispersion is anion or cation. The charge of the dispersion is preferably measured by particle microelectrophoresis.

Preferred charged flocculants may be cations or anions, i.e. polyelectrolytes with a total anion or cation charge. The polyelectrolyte contained in the aqueous solution suitably has a weight average molecular weight of at least about 6,000, preferably at least about 10,000, and is usually water dispersible or water soluble. Usually, its weight average molecular weight is about 10,000,000 or less, more preferably from about 100,000 to about 1,000,000. The polyelectrolyte may have a charge density of at least about 0.1 meq / g. Typical charge densities are from about 0.1 meq / g to about 18 meq / g, more preferably from about 0.1 meq / g to about 12 meq / g, typically from about 0.5 meq / g to about 6 meq / g. Range. Cationic or anionic polyelectrolytes may also have oppositely charged charged groups, commonly referred to as amphoteric polyelectrolytes. The charged polyelectrolyte is preferably selected from the group consisting of polysaccharides, vinyl addition polymers, condensation polymers, and mixtures thereof.

If the cationic polyelectrolytes are present in a solution containing a flocculant, they may be of the same type or a mixture of different cationic polyelectrolytes. Cationic polyelectrolytes are polysaccharides such as potato, starch that can be derived from corn, preferably a starch having a reaction product of a tertiary amine group, quaternary ammonium group or trimethylamine and epichlorohydrin, preferably a condensation polymer; A chain reaction polymer exemplified by vinyl addition polymers such as polyepihalohydrin, polyamidoamine, polyethyleneimine, etc., for example, from the group consisting of polyacrylamide, copolymers of acrylate and acrylamide, diallyldimethylammonium chloride polymer called polyDADMAC It is preferred to be selected.

Suitable anionic flocculants are selected from the group consisting of polyelectrolytes, silica-based particles, and mixtures thereof.

When an anionic polyelectrolyte is included in the coagulant solution, the anionic polyelectrolyte may constitute a mixture of different anionic polyelectrolytes or only a special anionic polyelectrolyte. The anionic polyelectrolyte is preferably selected from the group consisting of polysaccharides, condensation polymers and chain reaction polymers, preferably from the group consisting of polysaccharides, polysulfates, polysulfonates, and mixtures thereof. Suitable anionic polyelectrolytes are carboxylated celluloses such as carboxymethyl cellulose; phosphate modified polysaccharides such as starch; polyacrylates such as polyacrylamide; polysulfates exemplified by polyvinyl sulfate, polyethylene sulfate and the like; polyvinyl Polysulfonates such as sulfonates, lignin sulfonates, condensed naphthalene sulfonates.

As flocculants from the group of particles based on silica, ie SiO ₂ , inter alia colloidal silica, colloidal borosilicate, aluminum-modified silica or aluminum silicate, polyaluminosilicate microgels, and mixtures thereof Is mentioned. Silica-based particles are often referred to as silica sols. The particles may be colloids, such as the colloidal range of particle sizes, or preferably amorphous or substantially amorphous. Silica-based sols can also be modified and include other elements such as aluminum and / or boron, which can be present in the aqueous phase and / or silica-based particles. Suitable silica-based particles of this type include colloidal aluminum-modified silica and aluminum silicate. Mixtures of such suitable silica-based particles can also be used. The anionic silica-based particles are appropriately structured anionic silica sols, where the silica particles have a specific surface area in the range of 30-1200 m ² / g and typically 8-45%, Suitably it may have an S value in the range of 10-35%, preferably 10-30%. Specific surface area can be measured in a known manner, for example, by titration with NaOH as described by Sears in Analytical Chemistry 28 (1956): 12, 1981-1983 and US Pat. No. 5,176,891, while The S value of Iler, R. K. And Dalton, R.A. L. J. Phys. Chem. 60 (1956), 955-957, and can be measured and calculated. The S value is said to be a measure of the degree of agglomeration or microgel formation, and a low S value indicates a high microgel content and is seen as a measure of the amount (wt%) of SiO _{2 in} the dispersed phase. The structured sol silica particles are usually surface modified with aluminum to the extent of 2-25%, preferably 3-20%. The degree of aluminum surface modification means the number of aluminum atoms substituted for silicon atoms in the particle surface. The degree of modification is given in% and is calculated on the basis of 8 silanol groups per nm ² . This is described in Iller, R .; K. In Journal of Colloidal and Interface Science, 55 (1976): 1, 25-34. The S value shown for the sol is highly correlated with the particle size distribution.

The sol of cationic silica-based particles, ie, cationic silica-based particles, is typically one or different polyvalents including metal oxides, metal hydroxides and hydrated metal oxides. Positively charged particles having a dense silica core coated / modified with a metal-oxygen compound. Preferably, the silica particles are coated with a kind of polyvalent metal-oxygen compound, preferably trivalent and tetravalent metal-oxygen compounds such as aluminum, chromium, gallium, titanium and zirconium, whereby aluminum is particularly preferred. . Suitable anion counterions include halide ions, such as chloride ions, acetate ions or nitrate ions. Suitably, the positively charged colloidal silica particles are preferably inorganic silica particles which may be surface modified with aluminum, for example various oxides and hydroxides of aluminum. The positively charged silica particles can have a particle size of less than about 500 nm, usually greater than 1.0 nm. The specific surface area in the range of from about 5 to about 1800 m ² / g of silica particles, preferably about 30 to about 1200 m ² / g, more preferably may range from 50~1000m ² / g. The positively charged colloidal aluminum-modified silica particles are preferably in the range of 1:20 to 4: 1, preferably in the range of 1:10 to 2: 1, most preferably in the range of 1: 5 to 1: 1. having a weight ratio of _Al 2 _{O 3} pairs of SiO _2.

Suitable inorganic aluminum-containing compounds that act as flocculants are salts containing aluminum, such as aluminum sulfate, aluminum chloride and polyaluminum chloride, commonly referred to as alum, polyaluminum chloride compounds containing sulfate and polyaluminum hydroxysilicate sulfate. There are various inorganic polyaluminum compounds such as the fate compounds. Polyaluminum compounds are based on aluminum, hydroxy groups and anions, which are called basic and in aqueous solution they are polynuclear complexes.

Examples of polyaluminum compounds may have the general formula Al _n (OH) _m X _3n-m . Where X is a negative ion, such as a chloride ion or acetate ion, and both n and m are positive integers such that 3 _nm is greater than zero. X is preferably Cl ^- and such a polyaluminum compound is known as polyaluminum chloride (PAC). Polyaluminum chloride may also contain anions from sulfuric acid, phosphoric acid, polyphosphoric acid, chromic acid, dichromic acid, silicic acid, citric acid, carboxylic acid or sulfonic acid. An example of polyaluminum sulfate is the formula [Al (OH) _x (SO ₄ ) _y (H ₂ O) _z ] _n , where x has a value from 1.5 to 2.0, and y is 0.5 Having a value of ˜0.75, x + 2y = 3 and z = 1.5-4, preferably 1.5-3.0). Commercially available inorganic aluminum-containing compounds include, for example, Ecofloc manufactured and sold by Eka Chemicals AB, Zachtclar (registered trademark) sold by Zachleben Chemie in Germany, and sulfate containing by Atchem in France WAC, the highly basic polyaluminum chloride compound Rocron, sold by Hoechst AG in Germany, poly (hydroxyaluminum) sulfate omnickle, sold by Omnichem, USA, and near, sold by Nearset, USA Proof (which is aluminum hydroxyacetate) and Arzofix (which is based on polyaluminum chloride and dicyandiamide) sold by SKW Trostberg (Germany).

When an inorganic aluminum-containing compound is present in an aqueous dispersion of a sizing agent, the sizing agent can aggregate by changing the pH of the dispersion by the addition of a suitable acid or base. Usually, sizing dispersions containing aluminum-containing compounds are acidic, i.e. the dispersion has a pH in the range of 2-5. Therefore, the sizing agent is preferably increased by increasing the pH of the acidic dispersion to a neutral level (pH from 6 to 7.5) or even slightly alkaline (pH from 8 to 10). Flocculation can be triggered.

The type of sizing agent included in the aqueous dispersion is not critical and thus any sizing agent known to those skilled in the art, such as rosin, for example toughened and / or esterified rosin, wax,
Non-cellulose reactive agents including fatty acid and resin acid derivatives, such as fatty amides and fatty esters, such as glycerol triesters of natural fatty acids, and cellulose reactive agents may be used. However, the preferred sizing agent included in the aqueous dispersion is a cellulose reactive sizing agent. Suitable cellulose reactive sizing agents are the group consisting of hydrophobic ketene dimers, ketene dimer multimers, acid anhydrides, organic isocyanates, carbamoyl chloride and mixtures thereof, more preferably ketene dimers and acid anhydrides. And most preferably selected from ketene dimers. Suitable ketene dimers have the following general formula (I): In which R ¹ and R ² represent a saturated or unsaturated hydrocarbon group, usually a saturated hydrocarbon, which preferably has 8 to 36 carbon atoms, usually 12 to 20 carbons. A linear or branched alkyl group having an atom, for example, a hexadecyl group and an octadecyl group. The ketene dimer may be liquid at ambient temperature, eg, 25 ° C., preferably 20 ° C. In general, the acid anhydride may be characterized by the following general formula (II): In which R ³ and R ⁴ may be the same or different and preferably represent a saturated or unsaturated hydrocarbon group containing 8 to 30 carbon atoms, or R ³ and R 4 ⁴ can form a 5- to 6-membered ring together with the —C—O—C— moiety, and optionally further substituted with a hydrocarbon group containing up to 30 carbon atoms. Examples of commercially available acid anhydrides include alkyl succinic anhydrides and alkenyl succinic anhydrides, particularly isooctadecenyl succinic anhydride.

Suitable ketene dimers, acid anhydrides and organic isocyanates include the compounds disclosed in US Pat. No. 4,522,686, which is hereby incorporated by reference. Examples of suitable carbamoyl chlorides include those disclosed in US Pat. No. 3,887,427, which is also incorporated herein by reference.

Another preferred embodiment of the present invention is a paper sizing method comprising providing an aqueous suspension comprising cellulosic fibers, dewatering said aqueous suspension, thereby forming a paper web, said method Adding an aqueous composition comprising an agglomerate comprising a sizing agent to a cellulose suspension, wherein the composition comprises (i) an aqueous solution comprising at least an anionic flocculant prior to addition to the aqueous suspension And (ii) a paper sizing method characterized by being obtained by mixing a cationic aqueous dispersion containing a sizing agent in any order and having a zeta potential of the composition of less than 20 mV.

Accordingly, a preferred aqueous sizing composition of the present invention is an aqueous sizing composition comprising an agglomerate comprising a sizing agent, the composition comprising (i) a solution comprising at least one anionic flocculant, and (ii) a sizing agent. Is obtained by mixing in any order a cationic aqueous dispersion containing, the composition having a zeta potential of less than 20 mV.

Preferably, the anionic flocculant has an anionic polysaccharide, i.e. an anionic derivative of cellulose, e.g., usually having a charge density of about 0.5 to about 18 meq / g, more preferably about 1.0 to about 6 meq / g. Carboxymethylcellulose. The cationic aqueous dispersion preferably comprises a cationic polyelectrolyte, preferably a cationic condensation polymer exemplified by epihalohydrin type polymers (eg, polyamines), amidoamine type polymers and ethyleneimine type polymers. Depending on the monomer used, the cationic polymer may be branched or unbranched. Cationic polyelectrolytes have a charge density in the range of about 0.5 to about 20 meq / g, typically about 1.0 to about 12 meq / g, preferably about 1.0 to about 6 meq / g. It is preferable to have. Preferred cationic condensation polymers include polyamidoamines such as those produced from aliphatic amines and dicarboxylic acids, such as condensation of adipic acid, ethylenediamine or hexamethylenediamine and diethylenetriamine; polyamidoamine epichlorohydrin resin, polyethyleneimine And vinylamine type polymers. In general, when the charge density of one or more cationic polymers present in the dispersion and / or the charge density of the flocculant is increased, large particles containing a sizing agent are formed (good flocculation).

An aqueous composition containing an agglomerate containing a sizing agent is obtained by preparing a charged aqueous dispersion containing a sizing agent and an aqueous solution containing an aggregating agent and mixing them. Aqueous dispersions are produced by applying known dispersion / emulsification techniques. The dispersion is preferably produced by preparing a sizing agent in a molten form and dispersing the liquid sizing agent in an aqueous solution containing the dispersing agent using a high-pressure apparatus. If sizing agents that are solid at ambient temperature are used, they are melted prior to emulsification.

For aqueous solutions containing flocculants, these are produced by simply mixing a water-dispersible or water-soluble drug in an aqueous solution, optionally with a suitable dispersant. The amount of flocculant present in the solution is not critical. Suitably the amount of flocculant present in the solution is from about 0.01% to about 15% by weight. The aqueous dispersion mixed with the aqueous solution containing the flocculant typically has a sizing agent content of from about 0.1% to about 50% by weight, preferably from about 1.0% to 20% by weight. Have.

The sizing agent is present in the composition of all embodiments from about 0.01 wt% to about 20 wt%, preferably from about 0.07 wt% to about 5 wt%, more preferably based on the total composition. It is preferred that it be present in an amount from about 0.1% to about 2% by weight, while the flocculant is typically about 0.1% to about 10% based on the sizing agent in the composition. It is present in an amount up to wt%, preferably in the range of 0.1 wt% to 5 wt%.

The method of the present invention is used for paper manufacture. The term “paper” as used herein, of course, includes not only paper and its products, but also other products such as sheets or webs, such as boards and paperboard, and these products. The process can be used for the manufacture of paper from different types of suspensions of cellulose-containing fibers, the suspension preferably being at least 25% by weight of such fibers, preferably at least 50% by weight, based on dry matter Should be included. Suspensions are fibers from chemical pulps such as sulfate pulp, sulfite pulp and organosol pulp, both hardwood and softwood, mechanical pulp such as thermomechanical pulp, chemothermomechanical pulp, refiner pulp and groundwood pulp. And can be based on recycled fibers from deinked pulp and mixtures thereof if desired. The present invention is particularly useful for the production of paper from suspensions based on recycled fiber-containing pulp and deinked pulp, the cellulose fiber content of such sources being up to 100%, preferably from 20%. It may be up to 100%.

It has been found that the method of the present invention can also be used to size paper from suspensions containing cellulose fibers and optional fillers and having high cation requirements and / or high conductivity. If the cation requirement of the suspension is above about 1000 μeq / l, then the cation requirement of the suspension is also above about 2000 μeq / l, preferably above about 3000 μeq / l, preferably about 4000 μeq / l. If it is above, sufficient sizing of the paper is obtained. Furthermore, the conductivity of the raw material may be at least 0.20 mS / cm, preferably at least 3.5 mS / cm. Very good sizing results were observed at conductivity levels above 5.0 mS / cm and even above 7.5 mS / cm. The cation demand can be measured by polyelectrolyte titration (Mutek PC 02). Conductivity can be measured with conventional equipment, such as the WTW LF 539 equipment supplied by a Christian burner. The above values are preferably supplied to the head box of the paper machine or obtained by measuring the cation requirement or conductivity of the cellulose suspension present therein or by dehydrating the suspension. Measured by measuring the cation demand or conductivity of the produced white water. A high conductivity level means a high content of salt (electrolyte), in which the various salts are monovalent, such as alkali metals, for example Na ⁺ and K ⁺ , alkaline earths, for example Ca ²⁺ and Mg ^2+. Divalent and polyvalent cations, aluminum ions such as Al ³⁺ , Al (OH) ²⁺ and polyaluminum ions, and halide ions such as Cl ⁻ , sulfate ions such as SO ₄ ²⁻ and HSO _4. ^-, carbonate ion, e.g., CO ₃ ^2-and HCO 3 ^_-, 1-valent such as silicate ions and lower organic acids, can be based on divalent and polyvalent anions, whereas a high cation The requirement means a large amount of anionic polyelectrolyte, for example xylan. The present invention is particularly useful for the manufacture of paper from raw materials having a high content of divalent and polyvalent cation salts, usually with a cation content of at least 200 ppm, preferably at least 300 ppm, preferably at least 400 ppm. is there. Salt is used to produce raw materials, especially in an integrated mill where concentrated aqueous fiber suspensions from pulp mills are usually mixed with water to produce dilute suspensions suitable for papermaking in paper mills. Derived from cellulose fibers and fillers. The salt may also be derived from various additives introduced into the raw material, fresh water supplied to the process, or added from time to time. Furthermore, the salt content is usually high in a process in which white water is thoroughly circulated, which may result in a significant accumulation of salt in the water circulating in the process.

Furthermore, the present invention provides a thorough circulation of white water, i.e., a high degree of sealing of white water used per ton of dry paper from which 0-30 tons of fresh water is produced, typically less than 20 tons per ton of paper Preferably including less than 15 tons, preferably less than 10 tons, in particular less than 5 tons of paper-making process circulated with fresh water. The circulation of white water obtained in the process preferably comprises mixing white water with cellulose fibers and / or any filler to produce a suspension to be sized. It preferably comprises mixing white water with a suspension containing cellulose fibers and optional fillers before the suspension enters the sizing forming wire. Further, the present invention is illustrated by the following examples, which are not intended to limit the invention. Unless otherwise indicated, “%” represents “% by weight”.

In all examples, the weight average diameter of the particles containing the sizing agent was measured using a Malvern Mastersizer Microplus (Malvern Instruments) with a small volume cell top. The relative particle refractive index for ketene dimer (AKD) particles was set to 1.15, the imaginary refractive index was set to 0.1, and the refractive index for the dispersion medium (water) was set to 1.33. Data was analyzed according to the polydispersity model, 5OHD. The particle weight average diameter, ie the particle size distribution, was expressed as PSD D (v. 0.5), representing the volume weighted particle size where 50% of the particles were below that value. The amount of particles containing the sizing agent (floc) was calculated using a Coulter Counter Multisizer II (Coulter International, USA).

An aqueous solution containing 0.092 mg / l carboxymethylcellulose (CMC) having a charge density of 3.6 meq / g and a weight average molecular weight of 250,000 in 100 ml of potassium sulfate solution (0.3 g / l potassium sulfate), and b) A pre-agglomerated sizing composition was produced in accordance with the present invention by mixing a cationic sizing dispersion comprising conventional ketene dimer (AKD), cationic polyamine and naphthalene sulfonate. CMC solution was added to the dispersion in an amount to effect charge neutralization of the composition. The charge of the composition was measured using a PCD (Particle Charge Detector, Mutec PC02). The resulting sizing composition had a ketene dimer amount of 0.025%. The weight average diameter of the particles of the composition containing the ketene dimer sizing agent was around 30 μm. The composition agglomerates contained about 10% by volume sizing agent. The volume% was calculated as follows. The weight average particle diameter of the particles is 30 μm, which results in a particle volume of 1.4E-14 m ³ . The weight of the agglomerates was measured by dividing the total amount of sizing agent in a specific volume by the total amount of particles in that specific volume. The amount of particles was measured by use of a Coulter counter. The weight of one particle is calculated as 1.45E-12 kg to obtain an aggregate density (particle weight / particle volume) near 100 kg / m ³ . The density for the AKD used is 960 kg / m ³ . By dividing the density of the agglomerates by the density for AKD, a volume%, ie around 10% by volume, was obtained.

For comparison purposes, a non-aggregated cation ketene dimer sizing dispersion was prepared by using the same sizing dispersion that was pre-agglomerated but the sizing dispersion was not mixed with the CMC solution or potassium sulfate solution. . The weight average diameter of the ketene dimer particles was 0.77 μm.

The composition and dispersion comprises 60:40 weight ratio hardwood (HW) and softwood (SW) sulfate pulp, pH of 8.0, conductivity of 480 μS / cm, 0.511% based on dry fiber ( Sizing efficiency of the pre-agglomerated composition and the non-agglomerated dispersion by adding to the furnish in an amount apparent in Tables 1 and 2 having a concentration of w / w) and 0.3 g / l potassium sulfate. Evaluated. No retention aid was added to the suspension. A finish sheet former was used to form a paper sheet having a basis weight of 70 g / m ² .

The same ketene dimer sizing dispersion used in Example 1 was agglomerated by adding a solution of an anionic aluminum modified silica sol (NP590). A pre-agglomerated composition was prepared according to the method outlined in Example 1. The same paper suspension as in Example 1 was used.

A cation sizing dispersion containing 8.9% conventional ketene dimer sizing agent and 1.1% polyamidoamine having a charge density of 640 μeq / g was converted into a Brit Dynamic Dryage Jar (BDDDJ) (Paper. Agglomerated by the addition of 0.120 g CMC per gram of total dispersion. The resulting composition was stirred at 1000 rpm for 3 minutes. The same cation dispersion containing polyamidoamine but not pre-agglomerated was used for comparison purposes. The weight average diameter of the particles containing the sizing agent was 20 μm (preliminary aggregation composition) and 0.8 μm (non-aggregation dispersion).

By measuring the sizing efficiency of the pre-agglomerated composition and the cation dispersion by measuring the Cobb ₆₀ (SCAN-P 12:64) of the experimental sheet made in Formet Dynamic (Center Technique du Papierre, France) evaluated. Sheets were formed by adding the pre-agglomerated composition and the non-agglomerated composition to the raw materials in the amounts shown in Table 4 or Table 5, respectively. The stock comprises TCF (completely chlorine-free) birch pulp and has a concentration of 0.15% (w / w), a pH of 7.5-7.7 and a conductivity in the range of 1000-1200 μS / cm. Was.

Claims (24)

A paper sizing method comprising preparing an aqueous suspension comprising cellulose fibers, dehydrating the aqueous suspension, thereby forming a paper web, the method comprising applying a sizing agent to the cellulose suspension. Adding an aqueous composition comprising an agglomerate comprising, wherein the agglomerate has a weight average diameter of 15 μm to 250 μm, and the composition is (i) at least prior to addition to the aqueous suspension A paper sizing method obtained by mixing an aqueous solution containing a kind of flocculant and (ii) an aqueous dispersion containing a sizing agent in any order, and the composition has a zeta potential of less than 20 mV. .   The method of claim 1, wherein the zeta potential of the composition is less than 18 mV.   The method of claim 1, wherein the zeta potential of the composition is less than 15 mV. Weight average diameter of the aggregates is from 22μm to 250 [mu] m, method according to any of claims 1 to 3. The method according to any one of claims 1 to 4 , wherein the sizing agent is a cellulose-reactive sizing agent. 6. The method of claim 5 , wherein the cellulose reactive sizing agent is selected from the group consisting of ketene dimers, ketene dimer multimers, acid anhydrides, organic isocyanates, carbamoyl chlorides and mixtures thereof. 6. The method of claim 5 , wherein the cellulose reactive sizing agent is selected from the group consisting of ketene dimers and acid anhydrides. Flocculant is charged flocculant having an opposite charge to the aqueous dispersion, the method according to any of claims 1 to 7. 9. The method of claim 8 , wherein the charged flocculant is an anion and the charged aqueous dispersion is a cation. The method of claim 9 , wherein the anionic flocculant is selected from the group consisting of polyelectrolytes, silica-based particles, and mixtures thereof. The method of claim 9 , wherein the charged flocculant is an anionic polyelectrolyte. 12. The method of claim 11 , wherein the anionic polyelectrolyte is selected from the group consisting of polysaccharides, polysulfates, polysulfonates, and mixtures thereof. The method of claim 11 , wherein the anionic polyelectrolyte has a weight average molecular weight of at least 6000. 9. The method of claim 8 , wherein the charged flocculant is a cation and the charged aqueous dispersion is an anion. An aqueous sizing composition comprising an agglomerate comprising a sizing agent , wherein the agglomerate has a weight average diameter of 15 μm to 250 μm, the composition comprising (i) a solution comprising at least one flocculant; ii) An aqueous sizing composition obtained by mixing an aqueous dispersion containing a sizing agent in any order, wherein the composition has a zeta potential of less than 20 mV. The aqueous sizing composition of claim 15 , wherein the composition has a zeta potential of less than 18 mV. The aqueous sizing composition of claim 15 , wherein the composition has a zeta potential of less than 15 mV. The aqueous sizing composition of claim 15 , wherein the weight average diameter of the agglomerates is from 22 m to 250 m. The aqueous sizing composition of claim 15 , wherein the sizing agent is a cellulose reactive sizing agent. 20. The aqueous sizing composition of claim 19 , wherein the cellulose reactive sizing agent is selected from the group consisting of ketene dimers, ketene dimer multimers, acid anhydrides, organic isocyanates, carbamoyl chlorides and mixtures thereof. 21. The aqueous sizing composition of claim 20 , wherein the cellulose reactive sizing agent is selected from the group consisting of ketene dimers and acid anhydrides. The aqueous sizing composition of claim 15 , wherein the flocculant is a charged flocculant having an opposite charge relative to the aqueous dispersion. 23. The aqueous sizing composition of claim 22 , wherein the charged flocculant is an anion and the charged aqueous dispersion is a cation. 23. The aqueous sizing composition of claim 22 , wherein the charged flocculant is a cation and the charged dispersion is an anion.