JP2009538998A - Paper sizing method - Google Patents

Abstract

(A) preparing an aqueous cellulose suspension; (b) adding to the suspension (i) a nitrogen-containing organic compound having a molecular weight of less than 1,000; and (ii) a sizing agent reactive with cellulose. A method of making paper, and further comprising a nitrogen-containing organic having a molecular weight of less than 1,000, comprising the steps of adding separately and (c) dehydrating the resulting suspension to form paper A method as described above, wherein the compound is mixed with an aqueous dispersion of a sizing agent reactive with cellulose to form a premix and the premix is added to the suspension.
[Selection figure] None

Description

The present invention relates generally to a method for sizing paper and paperboard.

Cellulose-reactive sizing agents such as those based on alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA) to provide paper and paperboard with some resistance to wetting and penetration by aqueous liquids It is widely used at neutral or slightly alkaline stock pH during papermaking. Paper sizes based on cellulose and reactive sizing are generally applied in the form of a dispersion containing an aqueous phase and finely sized sizing particles or droplets dispersed therein.

When sizing agents that are reactive with cellulose are added to an aqueous cellulose suspension, generally low dosage sizing agents are used to provide a good sizing effect. The sizing effect begins to develop in the drying section of the paper machine. However, since most paper machines are operated at maximum speed to optimize paper production, the time in the drying section is often sufficient to produce sized paper while being run on the paper machine. It ’s not so long. Instead, the paper must be allowed to cure for 24 hours before a fully sized product is obtained. This slow development of the sizing effect causes a number of problems. First, subsequent operations such as printing, coating, pasting, etc. may be difficult to handle. Second, many papermakers constantly over-size the sizing agent to ensure that a fully sized product is obtained. As a result, problems with adhesion on machine parts are usually caused.

Patent Document 1 discloses a paper sizing accelerator that is a polymerization reaction product of a quaternary diallylammonium monomer and a diallylammonium monomer. The polymerization product has a molecular weight of at least 10,000. Patent Document 1 discloses that the paper sizing accelerator can be introduced into the paper furnish separately with the paper sizing agent during the paper making process or as an aqueous medium containing both components. ing.

U.S. Patent No. 6,057,031 discloses a sizing dispersion containing a sizing agent and a nonionic surfactant monoester of glycerol and a fatty acid.
WO 9710387 pamphlet International Publication No. 02081587 Pamphlet

It is an object of the present invention to provide a method for producing paper with improved initial sizing while being run on a paper machine. It is also an object of the present invention to provide a shorter cure time for the sizing agent. Further objects are described below.

The present invention
(A) providing an aqueous cellulose suspension;
(B) to the suspension,
(I) a nitrogen-containing organic compound having a molecular weight of less than 1,000, and (ii) separately adding a sizing agent reactive with cellulose, and (c) dehydrating the resulting suspension to paper A method of manufacturing paper, comprising the step of forming a paper.

The present invention further comprises (a) preparing a cellulose suspension;
(B) mixing a nitrogen-containing organic compound having a molecular weight of less than 1,000 with an aqueous dispersion of cellulose and a reactive sizing agent to form a pre-mixture;
(C) relates to a method of making paper comprising the steps of: adding the premix to the suspension; and (d) dehydrating the resulting suspension to form paper.

Surprisingly, according to the present invention, improved initial sizing by adding separately a nitrogen-containing organic compound having a molecular weight of less than 1,000 and a cellulose-reactive sizing agent to the cellulose suspension, ie It has been discovered that faster onset of sizing effect or faster curing of the paper can be achieved in papermaking. It has also been discovered that improved initial sizing can be achieved by adding a premix of the nitrogen-containing organic compound and an aqueous dispersion of a sizing agent reactive with cellulose to the suspension. Faster curing can give faster results to the sized product, minimize the risk of over-sizing the sizing agent, and can in turn result in less deposits on the paper machine. . In this way, improved operability of the paper machine can be achieved. Because of the faster cure time, less storage space will be required for the paper roll to be cured. The present invention thus provides substantial economic and technical benefits.

The nitrogen-containing organic compound according to the invention can be selected from primary amines, secondary amines, tertiary amines, quaternary amines, which are also called quaternary ammonium compounds. The nitrogen-containing compound is preferably water-soluble or water-dispersible, which can be aromatic, ie having one or more aromatic groups, or aliphatic. Organic compounds are usually preferred. The nitrogen-containing organic compound can be uncharged or cationic. Suitable nitrogen-containing organic compounds include acid addition salts of primary, secondary and tertiary amines and preferably quaternary ammonium compounds. The nitrogen-containing organic compound can have one or more oxygen-containing substituents, for example oxygen-containing substituents having oxygen in the form of hydroxyl groups and / or alkyloxy groups. Examples of preferred substituents of this type include hydroxyl groups such as ethanol groups, and methoxy and ethoxy groups. The nitrogen-containing organic compound can contain one or more nitrogen atoms, preferably 1 or 2 nitrogen atoms. The nitrogen-containing organic compound has a molecular weight of less than 1,000, suitably less than 900 or 800, preferably less than 750 or 600. Usually, the molecular weight of the nitrogen-containing organic compound is at least 250, preferably at least 330.

Examples of suitable nitrogen-containing organic compounds include those prepared by reacting primary, secondary or tertiary amines with methyl chloride, dimethyl sulfate and benzyl chloride. Examples of suitable quaternary ammonium compounds further include compounds having the general formula R ₄ N ⁺ X ^— , wherein each R is (i) hydrogen; (ii) a hydrocarbon group, preferably aliphatic And preferably an alkyl group having 1 to about 30 carbon atoms, preferably 1 to 22 carbon atoms; and (iii) a hydrocarbon group, suitably an aliphatic and preferably an alkyl group, of about Having up to 30 carbon atoms, preferably 4 to 22 carbon atoms, and one or more heteroatoms, such as oxygen or nitrogen, and / or groups having heteroatoms, such as interrupted by carbonyl and acyloxy groups; Here, at least 1, preferably at least 3, preferably all of the R groups have carbon atoms; suitably at least 1, preferably at least 2 of the R groups. , At least 7 carbon atoms, preferably selected from at least 9 carbon atoms, those having the most preferably at least 12 carbon atoms, independently of, and X ^- is an anion, typically a halide ion such as chlorine ion. The nitrogen-containing organic compound of the present invention is preferably substantially free of particles based on silica.

Examples of suitable primary amines, ie amines having one organic substituent, include alkylamines such as propylamine, butylamine, cyclohexylamine, alkanolamines such as ethanolamine, and alkoxyalkylamines such as 2-methoxyethylamine. . Examples of suitable secondary amines, ie amines having two organic substituents, include dialkylamines such as diethylamine, dipropylamine and diisopropylamine, dialkanolamines such as diethanolamine, and pyrrolidine. Examples of suitable tertiary amines, ie amines having 3 organic substituents are trialkylamines such as triethylamine, trialkanolamines such as triethanolamine, N, N-dialkylalkanolamines such as N, N-dimethylethanol. Contains amines. Examples of suitable quaternary ammonium compounds are methylbis [(tallow fatty acid) ethyl] -2-hydroxyethylammonium methylsulfate, dioctyldimethylammonium chloride, didecyldimethylammonium chloride, dicocodimethylammonium chloride, cocobenzyl Dimethylammonium chloride, coco (fractionated) benzyldimethylammonium chloride, octadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, dihexadecyldimethylammonium chloride, di (hydrogenated tallow) dimethylammonium chloride Di (hydrogenated beef tallow) benzylmethylammonium chloride, di (hydrogenated tallow fatty acid 2-hydroxyethyl ester) dimethylammonium chloride, (hydrogenated beef tallow) benzyldimethylammonium salt Including things, dioleyl dimethyl ammonium chloride, di (ethylene hexadecane carboxylate) dimethyl ammonium chloride, (vegetable oil) benzyl dimethyl ammonium chloride, a (dodecyl) benzyl dimethyl ammonium chloride and quaternized imidazole derivatives. Examples of suitable diamines include aminoalkylalkanolamines such as aminoethylethanolamine, piperazine, and piperazine substituted at nitrogen having 1 or 2 lower alkyl groups of 1 to 4 carbon atoms. Examples of suitable imidazoline derivatives are quaternary imidazolinium compounds such as 2- (C17 alkyl and C17 unsaturated alkyl) -1- [2- (C18 amide and C18 unsaturated amide) ethyl] -4,5-dihydro -1-methyl and methyl sulfate are included. Examples of preferred nitrogen-containing organic compounds are methylbis [(tallow fatty acid) ethyl] -2-hydroxyethylammonium methyl sulfate, di (hydrogenated tallow) dimethylammonium chloride, di (hydrogenated tallow fatty acid-2-hydroxyethyl) Ester) dimethylammonium chloride, didecyldimethylammonium chloride, (vegetable oil) benzyldimethylammonium chloride and (dodecyl) benzyldimethylammonium chloride.

The sizing agent reactive with cellulose can be selected from the group consisting of hydrophobic ketene dimers, ketene multimers, acid anhydrides, organic isocyanates and mixtures thereof, preferably ketene dimers, ketenes. Multimers and acid anhydrides, most preferably ketene dimers. Suitable ketene dimers have the following general formula (I), in which R ¹ and R ² are saturated or unsaturated hydrocarbon groups, usually saturated hydrocarbons, said hydrocarbon groups Are preferably straight-chain or branched alkyl groups having 8 to 36 carbon atoms, usually 12 to 20 carbon atoms, such as hexadecyl and octadecyl groups. Suitable acid anhydrides can be characterized by the following general formula (II), in which R ³ and R ⁴ can be the same or different and preferably contain 8-30 carbon atoms: Represents a saturated or unsaturated hydrocarbon group, or R ³ and R ⁴ together with the —C—O—C— moiety can form a 5- to 6-membered ring, optionally having up to 30 carbon atoms It may be substituted with a hydrogen group. Examples of commercially used acid anhydrides include alkyl and alkenyl succinic anhydrides, especially isooctadecyl succinic anhydride.

Suitable ketene dimers, acid anhydrides and organic isocyanates include the compounds disclosed in US Pat. No. 4,522,686, which is incorporated herein by reference.

The dispersion of the invention contains a dispersion or dispersion system comprising one or more dispersants and a protective colloid. Dispersants and protective colloids can be selected from anionic, nonionic, cationic and amphoteric compounds, which are dispersed or dispersed separately or together for sizing agents reactive with cellulose. Can function as a system. The dispersion according to the invention can have a content of sizing agent reactive with cellulose of from about 0.1% to about 30% by weight. The content of the sizing agent reactive with cellulose is suitably in the range of 5 to 25% by weight, preferably 8 to 20% by weight.

Dispersants and protective colloids can be any of those conventionally used in preparing aqueous sizing dispersions or emulsions. These can be selected from, for example, saponified rosin derivatives, alkyl sulfates, alkyl aryl sulfates, alkyl sulfonates, alkyl aryl sulfonates, and the like. Particularly suitable anionic dispersants are alkyl sulfates and alkyl sulfonates, such as sodium lauryl sulfate, and sodium lignosulfonate and sodium naphthalene sulfonate. Examples of suitable protective colloids include water-soluble cellulose derivatives such as hydroxyethyl and hydroxypropyl, methylhydroxypropyl and ethylhydroxyethylcellulose, methyl and carboxymethylcellulose, gelatin, starch, guar gum, xanthan gum, polyvinyl alcohol and the like. Examples of suitable nonionic dispersants can be selected from, for example, fatty alcohols, ethoxylated fatty alcohols, fatty acids, alkylphenols or fatty acid amides, ethoxylated or non-ethoxylated glycerol esters, sorbitan esters of fatty acids and the like. . Examples of suitable cationic dispersants and protective colloids include water-soluble nitrogen-containing epichlorohydrin resins and cationic starch. The dispersion may contain other additives such as preservatives. Suitably the amount of dispersant is at least 0.5% by weight per amount of sizing agent. Usually it is not necessary to use more than 10% by weight.

The nitrogen-containing organic compound of the present invention and the sizing agent reactive with cellulose can be added separately to the cellulose suspension in any order. The nitrogen-containing organic compound can be added separately before, simultaneously with, or after adding the sizing agent reactive with cellulose, preferably before adding the sizing agent reactive with cellulose.

An aqueous dispersion of a nitrogen-containing organic compound and a sizing agent reactive with cellulose, ie, also referred to herein as a sizing dispersion, can also be added as a premix to the cellulose suspension. In this embodiment, the nitrogen-containing organic compound and the sizing dispersion are mixed to form a premix prior to addition to the cellulose suspension. Shortly before the addition, mixing can take place by contacting the nitrogen-containing organic compound, suitably its aqueous phase, preferably its aqueous stream, with the sizing dispersion, preferably its aqueous stream.

The resulting aqueous phase or stream is then introduced into the cellulose suspension. Preferably, the contact time, i.e. the time from the mixing of the nitrogen-containing organic compound and the sizing dispersion to the addition of the premix thus formed to the cellulose suspension is short. This time can be less than about 20 minutes, suitably less than 4 minutes, preferably less than 2 minutes.

Mixing aqueous streams of nitrogenous organic compounds and sizing dispersions directs separate streams to be mixed toward each other, allowing them to invade each other, and the premixed stream formed in this way. It can be carried out by introducing it into a cellulose suspension. Preferably, the mixing is performed under turbulent conditions, which facilitates closer and faster mixing of both streams. Any mixing into which has at least two inlets through which the streams to be mixed are fed separately and through which at least one outlet through which the resulting premixture exits By means of the device both streams can be mixed, after which the premix is introduced into the cellulosic suspension. This stream mixing embodiment is advantageous from a practical point of view and provides operational benefits.

Nitrogen-containing organic compounds and cellulose-reactive sizing agents can be added to the cellulosic suspension at any location, for example, anywhere from the machine chest to the headbox.

Nitrogen-containing organic compounds and cellulose-reactive sizing agents can be added to the cellulose suspension in amounts that can vary within wide limits, and the dosage should be primarily pulped or sized. It depends on the quality of the paper, the sizing agent used that is reactive with cellulose and the level of sizing desired. The nitrogen-containing organic compound is suitably 0.005 to 0.5 wt%, preferably 0.01 to 0.3 wt%, most preferably 0.02 to 0.1 wt%, based on the dry weight of the cellulose suspension. Is added to the cellulosic suspension in an amount of%. The sizing agent reactive with cellulose is preferably added to the cellulose suspension in an amount of 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, based on the dry weight of the cellulose suspension. Is done.

The term “paper” as used herein refers not only to paper, but to all types of cellulose-based products in the form of sheets and webs (wet paper), such as cardboard, paperboard and in particular liquid packaging paperboard. Is also included. The process according to the invention can be used to produce paper from cellulose suspensions of various types of cellulose-containing fibers, which suspension is preferably at least 25% by weight, preferably at least 25% by weight per dry matter. Must contain at least 50% by weight of such fibers. The suspension comprises fibers from chemical pulps such as sulfate pulp, sulfite pulp and organosolv pulp, mechanical pulps such as thermomechanical pulp, chemical thermomechanical pulp, beaten pulp and groundwood pulp from both hardwood and softwood. And can also be based on recycled fibers, optionally from deinked pulp, and mixtures thereof. The cellulose suspension may optionally contain a mineral filler. Examples of conventional types of mineral fillers include kaolin, porcelain clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates such as chalk, ground marble and precipitated calcium carbonate. The pH of the cellulose suspension can be in the range of about 3 to about 10. The pH is suitably above 3.5, preferably in the range 4-9.

Chemicals conventionally added to cellulosic suspensions in papermaking, such as yield improvers, aluminum compounds, dyes, wet paper strength enhancing resins, fluorescent whitening agents, etc. are of course used in conjunction with the dispersions of the present invention. Can. Examples of aluminum compounds include alum, aluminate and polyaluminum compounds such as polyaluminum chloride and polyaluminum sulfate. Examples of suitable yield improvers are cationic polymers, anionic inorganic materials in combination with organic polymers such as bentonite in combination with cationic polymers, silica-based sols in combination with cationic polymers, or cationic and anions A functional polymer. Particularly good internal sizing can be obtained when the nitrogen-containing organic compound and the sizing agent reactive with cellulose are used in combination with a yield improver containing a cationic polymer. Suitable cationic polymers include cationic starch, guar gum, acrylate-based and acrylamide-based polymers, polyethyleneimine, dicyandiamine-formaldehyde resin, polyamine, polyamidoamine and poly (diallyldimethylammonium chloride) and combinations thereof Is included. Cationic polymers based on cationic starch and acrylamide are preferably used alone or in combination with each other or with other substances.

The invention will be further described in the following examples, which are not intended to limit the same.

AKD sizing of the liquid packaging board is performed on a laboratory paper machine, which includes a machine chest, two separate pumping equipment, a defoamer, a screen, a head box and a paper network, The cellulosic suspension was dehydrated in a papermaking net to form a sheet.

The nitrogen-containing organic compounds used in the following examples are those listed in Table 1.

The cellulose suspension contained 100% bleached CTMP. Two different nitrogen-containing organic compounds were used in tests A and E. The addition of nitrogen-containing compounds to the cellulose suspension was performed after the machine chest. A reference example was also implemented in which no nitrogenous organic compound was added. Cationic starch (Raisamyl 142) was dosed at two points: 2 kg / ton after the first pumping facility (P1) and 3 kg / ton before the second pumping facility (P2). AKD (Eka DH 28HF) sizing was metered before P2, and silica sol (Eka NP 442) was metered after P2 (3 kg / ton as received). The pH at the head box was 8.0.

An edge wick (EW) test with lactic acid (1%) was performed on the final paper after 1 hour and 24 hours, respectively.

As can be seen from Table 2, the test using the nitrogen-containing organic compound according to the present invention showed a lower EW value after 1 hour compared with the reference example not containing any nitrogen-containing organic compound. It can be concluded that the addition of nitrogen-containing organic compounds shortens the curing time. After 24 hours, all samples show roughly the same EW value.

The papermaking conditions were the same as in Example 1. Two different doses of nitrogen-containing organic compounds (0.25 kg / ton and 0.5 kg / ton) were tested at two dose levels of AKD (1 kg / ton and 1.5 kg / ton).

According to the Tappi T441 standard method, sizing performance was tested as Cobb ₆₀ value (Cobb water absorption) immediately after leaving the paper machine, 1 hour, 3 hours, and finally 24 hours later. The results are shown in Table 3.

Cobb ₆₀ value immediately after and one hour after leaving the papermaking machine the paper samples treated with nitrogen-containing organic compounds show lower Cobb ₆₀ value as compared to the Cobb ₆₀ value of the reference example. After 24 hours, all samples reached approximately the same sizing degree. From the results in Table 3, it can also be concluded that when the nitrogen-containing organic compound according to the invention is added to the suspension, the AKD dosage can be reduced.

For paper sheets treated with nitrogen-containing organic compounds, the tensile index (SCAN-P 67:93) was tested to see if the nitrogen-containing organic compounds had a detrimental effect on paper strength, and a reference example Compared with The results are shown in Table 4.

This result indicates that the nitrogen-containing organic compound does not have any significant effect on the tensile strength and therefore does not degrade the paper / board quality.

In this example, sizing performance was tested as Cobb ₆₀ values for paper when nitrogen-containing organic compounds were added in various addition modes. In addition, the sizing performance when using nitrogen-containing organic compounds and polyDADMAC polymers according to the present invention was tested.

The cellulose suspension contained 80% hardwood pulp and 20% softwood pulp and had a fiber concentration of 0.5%. No filler was added. The conductivity was 0.3 mS / cm and the pH was about 8. Handsheets were prepared according to the SCAN-C26: 76 standard method and sizing properties were measured as Cobb ₆₀ values according to the Tappi T441 standard method.

Calculated as dry matter per dry cellulosic suspension, used a first yield enhancement system containing 0.75 kg / ton cationic polyacrylamide (Eka PL 1510) and 1 kg / ton silica sol (Eka NP 442) It was done. Results are presented in Table 5. A second yield enhancement system containing 5 kg / ton of cationic potato starch (Perlbond 980) and 1 kg / ton of silica sol (Eka NP 442), calculated as dry matter per dry cellulose suspension, was used. Results are presented in Table 6.

When polyDADMAC (F) was added to the paper fiber suspension, the dosage of cationic polyacrylamide (Eka PL 1510) was reduced to 0.5 kg / ton.

The sizing agent AKD (Eka DR 28 HF) was added in an amount of 0.45 kg / ton, and the nitrogen-containing organic compound Arquad HTB-75 (C) according to the present invention was
a) 2 minutes before AKD,
b) premixed with AKD,
c) simultaneously with AKD or d) after AKD,
Was added at either.

The sizing results obtained by the addition of 0 kg / ton, 0.25 kg / ton and 0.5 kg / ton of the nitrogen-containing organic compound (C) are shown in Table 5 and Table 6, respectively. This result can be compared with the results obtained by the absence of nitrogen-containing organic compounds or the results obtained by adding polymer (F) instead of nitrogen-containing organic compounds according to the invention.

In this example, a liquid packaging board was prepared with the laboratory paper machine described in Example 1 and tested for sizing performance as a Cobb ₆₀ value according to the Tappi T441 standard method. The cellulose suspension contained 80% hardwood pulp (40% eucalyptus and 40% birch) and 20% softwood pulp and had a fiber concentration of 1.5%. No filler was added. The pH was 7.1. Calculated as dry matter per dry cellulose suspension, a yield-enhancing system containing cationic polyacrylamide (Eka PL 1510) 0.375 kg / ton and silica sol (Eka NP 442) 0.15 kg / ton is used. It was. Nitrogenous organic compounds Arquad HTB-75 (C) or Armosoft DEQ (G) according to the present invention were added before the sizing agent AKD (Eka DR 28 HF). Armosoft DEQ (G) was also added after the addition of the AKD in order to examine the effect of dispensing order on sizing performance. Sizing results are presented in Table Nos. 7 and 8, respectively. This result can be compared with the result obtained by the absence of nitrogen-containing organic compounds.

It can be seen that the nitrogen-containing organic compound according to the present invention has a favorable effect on the initial sizing of AKD. It is possible to reach the low Cobb ₆₀ value already immediately after the paper machine. The final sizing degree is not affected by the addition of nitrogen-containing organic compounds.

In this experiment, it can be seen that the nitrogen-containing organic compound can be added before or after the addition of AKD.

In this example, a liquid packaging board was prepared with the laboratory paper machine described in Example 1 and tested for sizing performance as a Cobb ₆₀ value according to the Tappi T441 standard method. The cellulosic suspension contained 100% bleached CTMP, which had a fiber concentration of 1.35%. No filler was added. The pH was 5.6 and the conductivity was 219 μS / cm. Nitrogen-containing organic compounds Arquad HTB-75 (C) or Armosoft DEQ (G) were used for the test. The addition of nitrogen-containing compounds to the cellulose suspension was done after the machine chest. Reference examples to which no nitrogen-containing organic compound was added were also carried out. Sizing AKD (Eka DR 28HF) was added in front of the second pumping facility (P2). Calculated as dry matter per dry cellulose suspension, cationic starch (Raisamyl 142) was added before P2 (5 kg / ton) and silica sol (Eka NP 442) was added after P2 (0. 15 kg / ton). Nitrogenous organic compounds Arquad HTB-75 (C) or Armosoft DEQ (G) according to the present invention were added before the sizing agent AKD (Eka DR 28HF).

It can be seen that the nitrogen-containing organic compound according to the present invention has a favorable effect on the initial sizing of AKD. It is possible to reach a low Cobb ₆₀ value already after 1 hour. The final sizing degree is not affected by the addition of nitrogen-containing organic compounds. The tensile index is not reduced by the addition of nitrogenous organic compounds.

About 0.05 to about 5 kg / ton calculated per dry pulp, preferably about 0.1 to about 3 kg / ton calculated per dry pulp, most preferably about 0.2 calculated per dry pulp. In an amount of ˜about 1 kg / ton, the nitrogen-containing organic compound according to the invention performs its function together with AKD.

Claims (18)

(A) providing an aqueous cellulose suspension;
(B) to the suspension,
(I) a nitrogen-containing organic compound having a molecular weight of less than 1,000, and (ii) separately adding a sizing agent reactive with cellulose, and (c) dehydrating the resulting suspension to paper A method of manufacturing paper, including the step of forming a paper. (A) preparing a cellulose suspension;
(B) mixing a nitrogen-containing organic compound having a molecular weight of less than 1,000 with an aqueous dispersion of cellulose and a reactive sizing agent to form a pre-mixture;
A method of making paper comprising the steps of (c) adding the premix to the suspension, and (d) dehydrating the resulting suspension to form paper. The process according to claim 1 or 2, wherein the nitrogen-containing organic compound is a quaternary ammonium compound. The process according to claim 1 or 2, wherein the nitrogen-containing organic compound is an amine or an acid addition salt thereof. Mixing contacts an aqueous stream of a nitrogen-containing organic compound having a molecular weight of less than 1,000 with an aqueous stream of a dispersion of sizing agent reactive with cellulose and the resulting stream into a cellulose suspension. The method according to claim 2, wherein the method is carried out by introducing. The process according to any one of claims 2 to 5, wherein the contact time between the nitrogen-containing organic compound and the aqueous dispersion of the sizing agent in the premix is less than 20 minutes before the addition. The process according to claim 1, wherein the nitrogen-containing organic compound is added to the cellulose suspension prior to adding the sizing agent reactive with cellulose. The process according to claim 1, wherein the nitrogen-containing organic compound is added to the cellulose suspension separately but simultaneously with the cellulose and the reactive sizing agent. The process according to claim 1, wherein the nitrogen-containing organic compound is added to the cellulose suspension after the addition of the sizing agent reactive with cellulose. Nitrogen-containing organic compounds are methylbis [(tallow fatty acid) ethyl] -2-hydroxyethylammonium methyl sulfate, di (hydrogenated tallow) dimethylammonium chloride, di (hydrogenated tallow fatty acid-2-hydroxyethyl ester) dimethylammonium 10. A process according to any one of the preceding claims comprising any one of chloride, didecyldimethylammonium chloride, (vegetable oil) benzyldimethylammonium chloride or (dodecyl) benzyldimethylammonium chloride. . The process according to any one of claims 1 to 9, wherein the nitrogen-containing organic compound comprises quaternary imidazolinium. 12. A process according to any one of the preceding claims, wherein the nitrogen-containing organic compound is substantially free of silica-based particles. 13. A process according to any one of claims 1 to 12, wherein the sizing agent reactive with cellulose is a ketene dimer. The process according to any one of claims 1 to 12, wherein the sizing agent reactive with cellulose is an acid anhydride. 15. A process according to any one of claims 1, 3, 4 and 7-14, wherein the sizing agent is added as an aqueous dispersion. The process according to any one of claims 1 to 15, wherein the nitrogen-containing organic compound is added in an amount of more than 20% by weight per weight of the sizing agent reactive with cellulose. The process according to any one of claims 1 to 16, wherein the nitrogen-containing organic compound is added in an amount of 0.005 to 0.5% by weight, based on the dry weight of the aqueous cellulose suspension. 18. A process according to any one of claims 1 to 17, wherein the sizing agent is added in an amount of 0.01 to 1.0% by weight, based on the dry weight of the aqueous cellulose suspension.