RU2194106C2 - Paper manufacturing process - Google Patents

Abstract

FIELD: paper-and-pulp industry. SUBSTANCE: paper is manufactured from suspension containing cellulose fibers and optionally fillers. Suspension is completed by dehydration and retention agents including cationic organic polymer containing aromatic group. The latter is added in amount at least 0.001% based on the weight solid pulp component. Suspension is further molded and dehydrated on screen, after which it shows conductivity at least 2.0 mC/cm. EFFECT: improved dehydration and retention. 16 cl, 8 tbl, 8 ex

Description

 The invention relates to the manufacture of paper, and more specifically to a method of manufacturing paper, in which a cationic organic polymer containing an aromatic group is added to the paper pulp. This method provides improved dehydration and retention.

BACKGROUND OF THE INVENTION
In papermaking, an aqueous suspension containing cellulosic fibers and optional fillers and additives, called paper pulp, is fed into a headbox, from which the pulp is pushed into a forming mesh. Water is drained from the pulp through a forming grid, so that a wet paper web is formed on this mesh, and this web is then dehydrated and dried in the drying zone of the paper machine. Water obtained from pulp dehydration, called white water, which usually contains fine particles, such as fine fibers, fillers and additives, is usually recycled during papermaking. The pulp is traditionally added with additives that facilitate dehydration and retention in order to accelerate the dehydration process and increase the adsorption of small particles on cellulose fibers so that they are retained in these fibers on the grid. Cationic organic polymers like cationic starch and cationic acrylamide-based polymers are widely used as dehydration and retention agents. These polymers can be used individually, but are more often used in combination with other polymers and / or anionic micronized materials, such as, for example, anionic mineral particles similar to colloidal silicon dioxide, colloidal silicon dioxide modified with aluminum, and bentonite.

 U.S. Patents 4,980,025; 5,368,833; 5,603,805; 5607552 and 5858174, as well as international patent application WO 97/18351, disclose the use of cationic and amphoteric polymers based on acrylamide and anionic mineral particles as pulp additives in papermaking. Now these additives are among the most effective dehydration and retention agents used. Similar systems are disclosed in European Patent Application 805234.

 However, it was noted that the performance of dehydration and retention aids containing organic cationic polymers deteriorate when they are used in pulps with a high salt content, i.e. with high electrical conductivity, and dissolved and colloidal substances. For such pulps, increased dosages of the cationic polymer are usually required, but, as a rule, the dehydration and retention effect achieved in this case is still insufficiently satisfactory. These problems are especially noticeable in paper mills, where recycle white water is widely used and only small amounts of fresh water are introduced, which leads to further accumulation of salts and colloidal materials in white water and the pulp to be dehydrated.

INVENTION
In accordance with the present invention, it has been found that improved dewatering and retention can be achieved in paper pulps containing high levels of salt (high electrical conductivity) and colloidal materials and / or in papermaking processes with a high white-water cycle closure when the agent is used for dehydration and retention, containing a cationic organic polymer containing an aromatic group. In particular, the present invention relates to a method for making paper from a suspension containing cellulosic fibers and optional fillers, comprising adding dehydration and retention agents to this suspension, including a cationic organic polymer, forming and dewatering the suspension on a mesh, the method being characterized in that cationic the organic polymer contains an aromatic group and is added in an amount of at least 0.001% based on the dry residue of the pulp, and the suspension, dehydrated on a grid, has a conductivity of at least 2.0 mS / cm.

 The specified technical result is achieved by a full set of features disclosed in paragraphs 1-16 of the claims.

 The result of the present invention is improved dehydration and / or retention in the case of the use of pulps having a high salt content and thus having a high level of conductivity and colloidal materials. The result of the present invention is also improved dehydration and / or retention in case of its implementation in paper production processes with extensive recycling of white water and limited introduction of fresh water and / or in processes involving the use of fresh water with a high salt content, in particular double and multivalent cations such as calcium. Thus, the present invention allows to increase the speed of the paper machine and to use lower dosages of additives that provide the corresponding effect of dehydration and / or retention, resulting in an improved papermaking process and economic benefits.

 The cationic organic polymer containing an aromatic group according to the present invention also referred to as the “base polymer” is capable of acting as a dehydrating and retention agent (agent). As used herein, the term “dehydrating and retentive agent” refers to one or more components (agents, agents or additives) which, when introduced into the pulp, give better dehydration and / or retention than those achieved in the absence of said one or more components. Accordingly, the base polymer provides improved dehydration and / or retention both when used alone and when used in combination with one or more additional pulp additives. The base polymer may be linear, branched or crosslinked, for example in the form of micronized material.

Preferably, the base polymer is water soluble or water dispersible. The aromatic group of the main polymer may be in the main polymer chain or, more preferably, it may be a side group attached or extending the main polymer chain, or may be contained in a side group that is attached or lengthening the polymer chain (main chain). Suitable aromatic (aryl) groups include those groups that contain a phenyl group, optionally substituted, a phenylene group, optionally substituted, and a naphthyl group, optionally substituted, for example, by groups having the general formula —C ₆ H ₅ , —C ₆ H ₄ -, -C ₆ H ₃ - and -C ₆ H ₂ -, for example, in the form of phenylene (-C ₆ H ₄ -), xylylene (-CH ₂ -C ₆ H ₄ -CH ₂ -), phenyl (- C ₆ H ₅ ), benzyl (—CH ₂ —C ₆ H ₅ ), phenethyl (—CH ₂ CH ₂ —C ₆ H ₅ ) and substituted phenyl (for example, —C ₆ H ₄ —U, —C ₆ H ₃ Y, and -C ₆ H ₂ Y _3), wherein one or more substituents (Y) attached to a phenyl ring may be selected from hydroxyl, halide, e.g., chloride, nitro, or hydrocarbyl groups containing from 1 to 4 carbon atoms.

где радикал R представляет собой Н или СН₃, и каждый из радикалов R₂ и R₃ представляет собой предпочтительно алкильную группу, содержащую от 1 до 3 атомов углерода, обычно от 1 до 2 атомов углерода; A₁ представляет собой О или NH; B₁ означает алкиленовую группу, содержащую от 2 до 8 атомов углерода, приемлемо от 2 до 4 атомов углерода, или гидроксипропиленовую группу; Q представляет собой заместитель, содержащий ароматическую группу, приемлемо фенильную или замещенную фенильную группу, которая может быть присоединена к атому азота через алкиленовую группу, обычно содержащую от 1 до 3 атомов углерода, приемлемо от 1 до 2 атомов углерода, и предпочтительно, когда Q означает бензильную группу (-СН₂-С₆Н₅), и X" представляет собой анионный противоион, обычно галогенида, такого как хлорид. Примеры пригодных для использования мономеров, описываемых общей формулой (l), включают четвертичные мономеры, полученные обработкой диалкиламиноалкил (мет)акрилатов, например диметиламиноэтил (мет)акрилата, диэтиламиноэтил (мет)акрилата и диметиламиногидроксипропил (мет)акрилата, и диалкиламиноалкил (мет)акриламидов, например диметиламиноэтил (мет)акриламида, диэтиламиноэтил (мет)акриламида, диметиламинопропил (мет)акриламида и диэтиламинопропил (мет)акриламида, бензилхлоридом. Предпочтительные катионные мономеры общей формулы (l) включают четвертичную соль диметиламиноэтилакрилата и бензилхлорида и четвертичную соль диметиламиноэтилметакрилата и бензилхлорида.The base polymer may be selected from homopolymers and copolymers derived from one or more monomers containing at least one monomer containing an aromatic group, an acceptable ethylenically unsaturated monomer, and the base polymer is suitably a vinyl addition polymer. As used herein, the term “vinyl addition polymer” refers to a polymer prepared by the addition polymerisation reaction of one or more vinyl monomers or ethylenically unsaturated monomers, which include, for example, acrylamide and acrylate monomers. Suitable base polymers include cationic vinyl addition polymers obtained by polymerization of a cationic monomer or a mixture of monomers comprising the cationic monomer described by the general formula (I)

where the radical R represents H or CH ₃ , and each of the radicals R ₂ and R ₃ represents preferably an alkyl group containing from 1 to 3 carbon atoms, usually from 1 to 2 carbon atoms; A ₁ represents O or NH; B ₁ means an alkylene group containing from 2 to 8 carbon atoms, suitably from 2 to 4 carbon atoms, or a hydroxypropylene group; Q is a substituent containing an aromatic group, an acceptable phenyl or substituted phenyl group, which can be attached to the nitrogen atom through an alkylene group, usually containing from 1 to 3 carbon atoms, acceptable from 1 to 2 carbon atoms, and preferably when Q means a benzyl group (—CH ₂ —C ₆ H ₅ ), and X ″ is an anionic counterion, usually a halide such as chloride. Examples of usable monomers described by general formula (l) include quaternary monomers obtained by the operation of dialkylaminoalkyl (meth) acrylates, for example dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and dimethylaminohydroxypropyl (meth) acrylate, and dialkylaminoalkyl (meth) acrylamides, for example dimethylaminoethyl (meth) acrylamide, diethylaminoethylamino acrylamide and diethylaminopropyl (meth) acrylamide, benzyl chloride. Preferred cationic monomers of the general formula (l) include dimethylaminoethyl acrylate and benzyl quaternary salt and dimethylaminoethyl methacrylate quaternary salt and ben ilhlorida.

где радикал R₄ представляет собой водород или группу СН₃; каждый из радикалов R₅ и R₆ означает водород или углеводородную группу, приемлемо алкил, содержащий от 1 до 6, приемлемо от 1 до 4 и обычно от 1 до 2 атомов углерода; А₂ означает кислород или NH; В₂ представляет собой алкиленовую группу, содержащую от 2 до 8 атомов углерода, приемлемо от 2 до 4 атомов углерода, или гидроксипропиленовую группу, или альтернативно оба радикала А и В не означают ничего, когда между С и N находится простая связь (O=C-NR₅R₆). Примеры пригодных для использования сополимеризуемых мономеров этого типа включают (мет)акриламид; мономеры на основе акриламида, подобные N-алкил(мет)акриламидам и N, N-диалкил(мет)акриламидам, например N-н-пропилакриламид, N-изопропил(мет)акриламид, N-н-бутил(мет)акриламид, N-изобутил(мет)акриламид и N-t-бутил(мет)акриламид; и диалкиламиноалкил(мет)акриламиды, например диметиламиноэтил(мет)акриламид, диэтиламино-этил(мет)акриламид, диметиламинопропил(мет)акриламид и диэтиламинопропил(мет)акриламид; мономеры на основе акрилата, подобные диалкиламиноалкил(мет)акрилатам, например диметиламиноэтил (мет)акрилат, диэтиламиноэтил(мет)акрилат, t-бутиламиноэтил(мет)акрилат и диметиламиногидроксипропилакрилат; и виниламиды, например N-винилформамид и N-винилацетамид. Предпочтительные сополимеризуемые неионные мономеры включают акриламид и метакриламид, т. е. (мет)акриламид, и основной полимер предпочтительно представляет собой полимер на основе акриламида.The base polymer may be a homopolymer obtained from a cationic monomer containing an aromatic group, or a copolymer obtained from a mixture of monomers including a cationic monomer containing an aromatic group and one or more copolymerizable monomers. Suitable copolymerizable nonionic monomers include those described by the general formula (II)

where the radical R ₄ represents hydrogen or a group of CH ₃ ; each of the radicals R ₅ and R ₆ means hydrogen or a hydrocarbon group, suitably alkyl containing from 1 to 6, suitably from 1 to 4 and usually from 1 to 2 carbon atoms; And ₂ means oxygen or NH; B ₂ represents an alkylene group containing from 2 to 8 carbon atoms, suitably 2 to 4 carbon atoms, or a hydroxypropylene group, or alternatively both radicals A and B mean nothing when there is a simple bond between C and N (O = C -NR ₅ R ₆ ). Examples of suitable copolymerizable monomers of this type include (meth) acrylamide; acrylamide-based monomers like N-alkyl (meth) acrylamides and N, N-dialkyl (meth) acrylamides, e.g. N-n-propylacrylamide, N-isopropyl (meth) acrylamide, N-n-butyl (meth) acrylamide, N isobutyl (meth) acrylamide and Nt-butyl (meth) acrylamide; and dialkylaminoalkyl (meth) acrylamides, for example dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and diethylaminopropyl (meth) acrylamide; acrylate-based monomers like dialkylaminoalkyl (meth) acrylates, for example dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate and dimethylaminohydroxypropyl acrylate; and vinylamides, for example N-vinylformamide and N-vinylacetamide. Preferred copolymerizable nonionic monomers include acrylamide and methacrylamide, i.e., (meth) acrylamide, and the base polymer is preferably an acrylamide-based polymer.

где радикал R₇ представляет собой водород или СН₃, каждый из радикалов R₈, R₉ и R₁₀ представляет собой водород или, что более предпочтительно, углеводородную группу, приемлемо алкил, содержащий от 1 до 3 атомов углерода, обычно от 1 до 2 атомов углерода; А₃ означает кислород или NH; В₃ представляет собой алкиленовую группу, содержащую от 2 до 4 атомов углерода, приемлемо от 2 до 4 атомов углерода, или гидроксипропиленовую группу, и X^- означает анионный противоион, обычно метилсульфат или галогенид, такой как хлорид. Примеры пригодных для использования катионных сополимеризуемых мономеров включают соли, полученные при добавлении кислоты, и четвертичные аммониевые соли диалкиламиноалкил(мет)акрилатов и диалкиламиноалкил(мет)акриламидов, упомянутых выше, обычно полученных при использовании таких кислот как HCl, H₂SO₄ и т.п. или агентов кватернизации, таких как метилхлорид, диметилсульфат и т.п.; и диаллилдиметиламмонийхлорид. Предпочтительные сополимеризуемые катионные мономеры включают четвертичную соль диметиламиноэтил(мет)акрилата и метилхлорида и диаллилдиметиламмонийхлорид. Могут быть также использованы сополимеризуемые анионные мономеры, такие как акриловая кислота, метакриловая кислота, различные сульфированные виниловые мономеры и т.п., предпочтительно в малых количествах.Suitable copolymerizable cationic monomers include those described by the general formula (III)

where the radical R ₇ represents hydrogen or CH ₃ , each of the radicals R ₈ , R ₉ and R ₁₀ represents hydrogen or, more preferably, a hydrocarbon group, suitably alkyl containing from 1 to 3 carbon atoms, usually from 1 to 2 carbon atoms; And ₃ means oxygen or NH; B ₃ represents an alkylene group having from 2 to 4 carbon atoms, suitably from 2 to 4 carbon atoms or a hydroxypropylene group, and X ^- is an anionic counterion, usually methylsulphate or a halide like chloride. Examples of suitable cationic copolymerizable monomers include acid-added salts and quaternary ammonium salts of dialkylaminoalkyl (meth) acrylates and dialkylaminoalkyl (meth) acrylamides mentioned above, usually obtained using acids such as HCl, H ₂ SO ₄ , etc. P. or quaternization agents such as methyl chloride, dimethyl sulfate and the like; and diallyldimethylammonium chloride. Preferred copolymerizable cationic monomers include a quaternary salt of dimethylaminoethyl (meth) acrylate and methyl chloride and diallyldimethylammonium chloride. Copolymerizable anionic monomers such as acrylic acid, methacrylic acid, various sulfonated vinyl monomers and the like can also be used, preferably in small amounts.

 The base polymer according to the present invention can be obtained from a mixture of monomers, usually containing from 1 to 99 mol%, suitably from 2 to 50 mol. %, and preferably from 5 to 20 mol.% of a cationic monomer containing an aromatic group, preferably described by the general formula (I), and from 99 to 1 mol.%, acceptable from 98 to 50 mol.%, and preferably from 95 to 80 pier % of other copolymerizable monomers, which preferably include acrylamide or methacrylamide ((meth) acrylamide), the monomer mixture suitably contains from 98 to 50 mol% and preferably from 95 to 80 mol% of (meth) acrylamide, the amount of percent is 100.

 The base polymer may also be selected from among polymers prepared by the condensation reaction of one or more monomers containing an aromatic group. Examples of such monomers include toluene diisocyanates, bisphenol A, phthalic acid, phthalic anhydride and the like, which can be used in the preparation of cationic polyurethanes, cationic polyamidamines, etc.

 In another embodiment or additionally, the base polymer may be an aromatic modified polymer using an aromatic group containing agent. Suitable modifying agents of this type include benzyl chloride, benzyl bromide, N- (3-chloro-2-hydroxy-propyl) -N-benzyl-N, N-dimethylammonium chloride and N- (3-chloro-2-hydroxypropyl) pyridine chloride. Suitable polymers for such aromatic modification include vinyl coupling polymers. If such a polymer contains a tertiary nitrogen atom, which can be quaternized with a modifying agent, the use of such agents usually leads to the polymer becoming cationic. Conversely, the polymer to be aromatically modified may be a cationic, for example, a cationic vinyl addition polymer.

 Typically, the charge density of the base polymer is in the range of 0.1 to 6.0 meq / g of dry polymer, suitably 0.2 to 4.0, and preferably 0.5 to 3.0.

 The weight average molecular weight of the synthetic base polymers is usually not less than about 500,000, suitably more than about 1,000,000, and preferably more than about 2,000,000. The upper limit is not critical; it may be approximately 50,000,000, typically 30,000,000 and suitably 2,500,000.

 The base polymer of the present invention can be in any state of aggregation, for example, in solid form, for example, in powder form, in liquid form, for example, in the form of solutions, emulsions, dispersions, including salt dispersions, etc. Examples suitable for use in the present invention basic polymers include those described in US patent 5169540; 5708071 and European Patent Applications 183466; 525751 and 805234, the essence of which is incorporated into this description by reference. When added to the pulp, the base polymer is suitably in liquid form, for example, in the form of an aqueous solution or dispersion.

 The base polymer can be added to the pulp to be dehydrated in amounts that can vary widely depending on inter alia, pulp type, salt content, salt type, filler content, filler type, injection point, etc. Typically, the base polymer is added in an amount that provides better retention compared to that achieved without administration. The base polymer is usually added in an amount of at least 0.001%, often at least 0.005% by weight, based on the dry pulp residue, with an upper limit of usually 3% and an acceptable 1.5% by weight.

 In a preferred embodiment of the present invention, the base polymer is used in combination with an additional pulp additive, thereby providing a dehydration and retention aid comprising two or more components, commonly referred to as dehydration and retention aids. As used herein, the term “dehydration and retention aids” refers to two or more components (agents, agents or additives) that, when introduced into the pulp, give better dehydration and retention than that achieved without the addition of these components. Examples of suitable pulp additives of this type include anionic micronized materials, for example, anionic organic particles and anionic mineral particles, water-soluble anionic vinyl addition polymers, low molecular weight cationic organic polymers, aluminum compounds, and combinations thereof. In a preferred embodiment of the present invention, the base polymer is used in combination with an anionic micronized material, mainly anionic mineral particles. In another preferred embodiment, the base polymer is used in combination with anionic mineral particles and a low molecular weight cationic organic polymer. In yet another preferred embodiment, the base polymer is used in combination with anionic mineral particles and an aluminum compound.

Anionic mineral particles that can be used according to the present invention include anionic particles based on silicon dioxide and smectite type kaolins. Preferably, the anionic mineral particles are in the size range of colloidal particles. Silica-based anionic particles, i.e. particles based on SiO ₂ or silicic acid are preferably used, and such particles are usually supplied in the form of aqueous colloidal dispersions, so-called sols.

 Examples of suitable particles based on silicon dioxide include colloidal silicon dioxide and various types of polysilicic acid. Silica-based sols can also be modified to contain other elements, such as aluminum and / or boron, which may be contained in the aqueous phase and / or in the silica-based particles. Suitable silica particles of this type include colloidal, aluminum-modified silica and aluminum silicates. Mixtures of such suitable silica particles may also be used. Dehydration and retention aids including suitable silica-based anionic particles are disclosed in US Pat. Nos. 4,388,150; 4,927,498; 4,954,220; 4,961,825; 4980025; 5,277,994; 5,167,891; 5,368,833; 5,447,604; 5,470,435; 5,543,014; 5,571,494; 5,573,674; 5,584,966; 5,603,805; 5688482 and 5707493, which are given in this application by reference.

The silica-based anion particles suitably have an average particle size of less than about 50 nm, preferably less than about 20 nm, and more preferably in the range of about 1 to about 10 nm. As is customary in silicon dioxide chemistry, particle size refers to the average size of primary particles that may or may not be aggregated. The specific surface area of the silica-based particles is suitably about 50 m ² / g and preferably more than 100 m ² / g. Typically, the specific surface area can be up to about 1700 m ² / g, and preferably up to 1000 m ² / g. The specific surface can be measured by titration with NaOH in a known manner, for example, as described by Sears in Analytical Chemistry 28 (1956); 12, 1981-1983 and in US patent 5176891. Thus, this specific surface area represents the average specific surface area of the particles.

In a preferred embodiment of the present invention, the anionic mineral particles are silica-based particles having a specific surface area in the range of 50 to 1000 m ² / g, preferably 100 to 950 m ² / g. This type of silica particle sol also encompasses modified sols, such as silica-based aluminum sols and silica-boron sols. Preferably, the particles based on silicon dioxide are present in the ash having an S-value in the range from 8 to 45%, preferably from 10 to 30%, and containing particles based on silicon dioxide with a specific surface area in the range from 300 to 1000 m ² / g, suitably from 500 to 950 m ² / g, and preferably from 750 to 950 m ² / g; as noted above, such sols can be modified with aluminum and / or boron. For example, the surface of the particles can be modified with aluminum to a degree of from 2 to 25% of the substitution of silicon atoms. S-value can be measured and calculated as described by Iler & Dalton in J. Phys. Chem. 60 (1956), 955-957. The S-value indicates the degree of aggregation or microgel formation, and lower S-values indicate a higher degree of aggregation.

In another preferred embodiment of the present invention, the silica particles are selected from polysilicic acid and a modified polysilicic acid having a high specific surface area, suitably above about 1000 m ² / g. The specific surface area can be in the range of 1000 to 1700 m ² / g, and preferably 1050 to 1600 m ² / g. The modified polysilicic acid sols may contain other elements, for example aluminum and / or boron, which may be in the aqueous phase and / or in particles based on silicon dioxide. In this chemistry, polysilicic acid is also referred to as polymeric silicic acid, polysilicic acid microgel, polysilicate and polysilicate microgel, which are all encompassed by the term polysilicic acid used in this application. Aluminum-containing compounds of this type are often also referred to as polyaluminosilicate and polyaluminosilicate microgel, both of which are encompassed by the terms colloidal, aluminum-modified silica and aluminum silicate as used herein.

Smectite type clays that can be used in the method of the present invention are known and include natural, synthetic and chemically treated materials. Examples of usable smectite clays include montmorillonite / bentonite, hectorite, beidelite, nontronite and saponite, preferably bentonite, and especially bentonite which preferably has a specific surface area of 400 to 800 m ² / g after swelling. Suitable clays are disclosed in US Pat. Nos. 4,753,710; 5071512 and 5607552, which are incorporated into this application by reference.

 Anionic organic particles that can be used according to the present invention include highly crosslinked anionic vinyl polymers of addition, suitably copolymers comprising an anionic monomer such as acrylic acid, methacrylic acid, and sulfonated or phosphonated vinyl addition monomers, usually copolymerizable with nonionic monomers such as (meth) acrylamide, alkyl (meth) acrylates, etc. Suitable anionic organic particles also include a ionic condensation polymers, for example, melamine-sulfonic acid sols. Water-soluble anionic vinyl addition polymers that can be used according to the present invention include copolymers containing anionic monomers such as acrylic acid, methacrylic acid and sulfonated vinyl addition monomers, usually copolymerizable with nonionic monomers such as acrylamide, alkyl acrylates, etc. for example, those disclosed in US patents 5098520 and 55185062, the essence of which is incorporated into this description by reference.

 Low molecular weight (hereinafter referred to as HMM) cationic organic polymers that can be used according to the present invention include those that are commonly referred to and used as anionic waste bins (AMUs). AMUs are known as neutralizing and / or fixing agents for harmful anionic substances present in the pulp, and their use in combination with dehydration and retention agents often provides further improvement in dehydration and retention. HMM cationic organic polymer may be natural or synthetic, and preferably it is HMM synthetic polymer. Suitable organic polymers of this type include HMM high charge cationic organic polymers such as polyamines, polyamidoamines, polyethyleneimines, diallyldimethylammonium chloride homo- and copolymers, (meth) acrylamides and (meth) acrylates. With regard to the molecular weight of the base polymer, the molecular weight of the NMM of the cationic organic polymer is preferably lower, it is suitably not less than 2000, and preferably not less than 10000. The upper limit of the molecular weight is usually about 700000, about 500000 is acceptable, and usually about 200000.

 Aluminum compounds that can be used according to the present invention include alum, aluminates, aluminum chloride, aluminum nitrate and polyaluminium compounds, such as polyaluminium chlorides, polyaluminium sulfates, polyaluminium compounds containing both ions - chloride and sulfate, polyaluminium silicate sulfates and their mixtures. Polyaluminium compounds may also contain other anions other than the chloride ion, for example, anions from sulfuric acid, phosphoric acid, organic acids such as citric acid and oxalic acid.

 The components of the dewatering and retention agents of the present invention can be added to the pulp in the usual manner and in any order. When using dehydrating and retention agents including a base polymer and anionic micronized material, mainly anionic mineral particles, it is preferable to introduce the main polymer into the pulp before introducing the micronized material, even if the reverse order of administration can be used. It is also preferable to introduce the base polymer prior to the shear stage, which can be selected from pumping, mixing, clarification, etc. , and introduce anionic particles after such a shear step. When using HMM, a cationic organic polymer or aluminum compound, such components are preferably added to the pulp before the introduction of the base polymer, optionally used in combination with anionic micronized material. Conversely, HMM cationic organic polymer and the base polymer can be introduced into the pulp almost simultaneously, either individually or in a mixture, for example, as disclosed in US patent 5858174, which is incorporated herein by reference. HMM cationic organic polymer and the base polymer are preferably introduced into the pulp before the introduction of the anionic micronized material.

 The dehydrating and retaining agent (a) according to the present invention can be introduced into the pulp to be dehydrated in quantities that can vary widely depending on inter alia, type and number of components, type of pulp, salt content, type of salts, filler content, type of filler , points of introduction, degree of recirculation of white water, etc. Typically, this agent (a) is added in amounts that provide better dehydration and / or retention than are achieved in the absence of these components. The base polymer is usually added in an amount of at least 0.001%, often at least 0.005% by weight based on the dry weight of the pulp, and the upper limit is usually 3% and an acceptable 1.5% by weight. Similar amounts are acceptable for water soluble anionic vinyl addition polymers, if any. When anionic micronized material is used in the process, the total amount introduced is usually not less than 0.001% by mass, often not less than 0.005% by mass, based on the dry pulp residue, and the upper limit is usually 1.0% and acceptable 0 6% by weight.

When silicon dioxide-based anionic particles are used, their total input amount is suitably in the range of 0.005 to 0.5% by weight, based on SiO _2, by weight of the dry pulp residue, preferably in the range of 0.01 to 0.2 % by weight. When using a cationic organic polymer in the NMM method, it can be added in an amount of at least 0.05% based on the dry weight of the pulp to be dehydrated. It is acceptable when this amount is a value lying in the range of values from 0.07 to 0.5%, preferably in the range of values from 0.1 to 0.35%. In the case when an aluminum compound is used in the implementation of the present method, its total amount introduced into the pulp to be dehydrated depends on the type of aluminum compound used and other expected effects. For example, it is well known that aluminum compounds are used as precipitants for rosin-based sizing agents. Typically, the total amount administered is at least 0.05% based on Al ₂ O ₃ and dry weight. It is acceptable when this amount is in the range of 0.5 to 3.0%, preferably in the range of 0.1 to 2.0%.

The method of the present invention is preferably used in the manufacture of paper from a suspension containing cellulosic fibers and optional fillers, i.e. pulp, which has a high conductivity. Typically, the specific conductivity of the pulp that is dehydrated on the grid is not less than 2.0 mS / cm, acceptable not less than 5.0 mS / cm, and most preferably not less than 7.5 mS / cm. The conductivity can be measured on standard equipment, such as, for example, the WTW LF 539 instrument supplied by Christian Berner. The above values are reasonably determined by measuring the specific conductivity of the cellulosic suspension, which is fed into or which is located in the pressure vessel of the paper machine, or, conversely, by measuring the specific conductivity of white water obtained by dewatering the suspension. High levels of conductivity indicate a high content of salts (electrolytes), while various salts can be based on mono-, bi- and multivalent cations, such as alkali metal cations, such as Na ⁺ and K ⁺ , alkaline earth metals, such as Ca ²⁺ and Mg ²⁺ , aluminum ions, for example Al ³⁺ , Al (OH) ²⁺ and polyaluminium ions, and mono-, di- and multivalent anions, such as halides, for example Сl ^- , sulfates, for example SO ₄ ^2- and HSO ₄ ^- , carbonates, for example СО ₃ ^{2 -} and НСО ₃ ^- , silicates and lower organic acids. The present invention is particularly applicable to the production of pulp paper having a high salt content of divalent and multivalent cations, and typically the content of divalent and multivalent cations is not less than 200 parts per million, acceptable not less than 300 parts per million, and preferably not less than 400 parts per million. Salts can be taken from the pulp preparation stage, i.e. from materials used in the preparation of pulp, for example water, cellulose fibers and fillers, in particular in separate plants where concentrated aqueous fiber suspensions from a paper mill are usually mixed with water and a diluted suspension suitable for making paper in a paper mill is obtained. Various additives introduced into the pulp, fresh water supplied to the process, etc. can also be a source of salt. In addition, the salt content is usually higher in those processes in which extensive white water is recycled, which can lead to a significant accumulation of salts in the water circulating in the process.

 Further, the present invention encompasses paper making processes in which white water is widely recycled, i.e. with a high degree of use of white water, for example, where 0 to 30 tons of fresh water per ton of dry paper are used, usually less than 20, acceptable less than 15, preferably less than 10, and noticeably less than 5 tons of fresh water per ton of paper. Recycling the white water obtained in the process, suitably includes mixing white water with cellulosic fibers and / or optional fillers to form a suspension to be dehydrated; preferably, when it involves mixing white water with a slurry containing cellulosic fibers and optional fillers, before the slurry enters the dewatering mold. White water may be mixed with the suspension before, between, simultaneously with or after the introduction of the components of the dehydrating and retention agents, if any; and before, simultaneously with or after administration of the base polymer. Fresh water can be introduced into the process at any stage: for example, it can be mixed with cellulose fibers in order to obtain a suspension, and it can be mixed with a suspension containing cellulose fibers in order to dilute it so that a suspension to be dehydrated forms until simultaneously with or after mixing the pulp with white water and before, between, simultaneously with or after the introduction of the components of the dehydrating and retention agents, if any, and before, simultaneously with or after the introduction of the main polymer.

 Of course, other additives that are traditional for the papermaking industry can be used in combination with the additives of the present invention, such as, for example, dry strength agents, wet strength agents, optical brighteners, dyes, sizing agents, such as rosin-based sizing agents and cellulose-reactive sizing agents, for example ketene dimers and succinic anhydrides, etc. The cellulosic suspension or pulp may also contain conventional mineral fillers, such as, for example, kaolin, Chinese clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates, such as chalk, ground marble and precipitated calcium carbonate.

The method of the present invention is used to make paper. Used in the present description, the term "paper" certainly includes not only paper and its production, but also containing cellulose fiber sheet or roll products, such as, for example, cardboard (weighing up to 250 g / cm ³ ) and thin cardboard and their manufacture. This method can be used to make paper from various types of suspensions of cellulose-containing fibers, and such suspensions should suitably contain not less than 25% by weight, and preferably not less than 50% by weight of such fibers based on the dry residue. These suspensions can be based on fibers from chemical pulp, for example sulfate, sulfite and organosolve pulp, mechanical pulp, such as thermomechanical pulp, chemothermomechanical pulp, refiner pulp and wood fiber pulp from both coniferous and deciduous wood, and can also be based on secondary fibers, optionally from pulp masses after removal of paint and mixtures thereof.

 The invention is further illustrated by the following examples, which, however, do not limit the scope of its claims. Parts and% refer to parts by weight and% by weight, respectively, unless otherwise indicated.

EXAMPLE 1 (comparative)
The dewatering and retention effects were evaluated using a Dinamic Drainage Analyzer (DDA), a dynamic dewatering analyzer supplied by Akribi, Sweden, which measures the dewatering time of a certain amount of pulp passing through the mesh after removing the plug and creating a vacuum on the opposite side of the mesh on which the pulp is located.

Use a paper composition based on 70% by weight of the pulp from the bleached birch-pine sulfate (60/40) mass, ennobled to 200 ^o CSF, and 30% by weight of crushed marble. The loading volume is 800 ml, a consistency of 0.3% and a pH of about 8.

 The specific conductivity of the mixture was adjusted to 0.47 mS / cm by adding sodium sulfate. The mixture was mixed in a vessel with a flow turbulizer at a speed of 1500 rpm for the entire experiment, and chemical additives were introduced as follows: i) the cationic polymer was introduced into the mixture, followed by stirring for 30 s, ii) the anionic mineral particles were introduced into the mixture with followed by stirring for 15 s, iii) dehydration of the mixture, automatically recording the dehydration time.

 The polymers used in the series of experiments were a P1 cationic copolymer obtained by polymerization of acrylamide (90 mol%) and acryloxyethyl dimethylbenzylammonium chloride (10%) and having an average molecular weight of about 6,000,000; and a P2 cationic copolymer obtained by the polymerization of acrylamide (90 mol%) and acryloxyethyltrimethylammonium chloride (10 mol%) and having an average molecular weight of about 6000000. Polymers P1 and P2 were dissolved in water and used as 0.1% aqueous solutions.

The anionic mineral particles used are silica-based particles of the type disclosed in US Pat. No. 5,368,833. The sol had an S value of about 25% and contained silica particles with a specific surface of about 900 m ² / g that were surface modified with aluminum to a degree of 5% . Silica-based particles are added in an amount of 1.0 kg / ton based on SiO ₂ and the dry residue of the mixture.

 Table 1 presents the values of the dehydration time at various dosages P1 and P2, calculated by the dry polymer of the dry residue of the mixture.

EXAMPLE 2 (comparative)
The effect of dehydration and retention was evaluated using DDA, as in example 1, in combination with a nephelometer. The retention of the first pass (mixture) is assessed by measuring the turbidity of the filtrate, white water obtained by draining the pulp.

A paper composition was used based on 56% by weight of pulp bleached with TMT / SGW peroxide (80/20), 14% by weight of bleached birch-pine sulfate pulp (60/40), enriched to 200 ^° CSF, and 30% by weight of Chinese clay . 40 g / l of colloidal fraction, bleached water from the SC plant, filtered through a 5 μm sieve and concentrated on a UV filter, 200000 fraction was added to the pulp. The volume of the mixture was 800 ml, the consistency was 0.14%, and the pH was adjusted to 4 , 0 with dilute sulfuric acid. The specific conductivity is controlled by the addition of calcium chloride (60 parts per million Ca ²⁺ ), magnesium sulfate (18 parts per million Mg ²⁺ ) and sodium bicarbonate (134 parts per million HCO ₃ ^- ).

In this series of experiments, polymers and anionic mineral particles are similarly used, as in Example 1. Two dosages of polymers are used, 1 kg / t and 2 kg / t, respectively, based on the dry polymer of the dry pulp residue. Table 2 shows the dependence of dehydration and retention on different dosages of particles based on silicon dioxide based on SiO ₂ and dry pulp residue.

EXAMPLE 3
In this series of experiments, the effect of dehydration and retention was evaluated according to the method described in example 2.

 The same paper composition was used as in Example 2. The loading volume was 800 ml and a pH of about 7. The conductivity was adjusted by the addition of calcium chloride, thereby simulating a very high electrolyte content and a high degree of use of white water.

 The polymers and anionic mineral particles of Example 1 were similarly used in this series of experiments.

Table 3 presents data on the effect of various dosages of particles based on silicon dioxide on the effect of dehydration and retention, calculated on SiO ₂ and based on the dry residue of paper pulp.

EXAMPLE 4
In this series of experiments, the dehydration effect is evaluated using the Canadian Standart Freeness Tester, which is the standard method for evaluating dehydration according to SCAN-C 21:65. All chemical additives are introduced into the Britt Dynamic Drainage Jar with a closed outlet at a stirring speed of 1000 rpm. / min for 45 s in accordance with the procedure described in example 1, and the paper mixture was then transferred to a Freeness device. At the same time, the smallest hole in the bottom of the Freeness is closed and the filtration time of 400 ml of the paper composition is measured through a mesh filter. The mixture is taken from a recycled waste paper recycling plant. The consistency is 0.14%, the specific conductivity is 8.0 mS / cm and the pH is approximately 7. Table 4 presents data showing the effect of different dosages of particles based on silicon dioxide, calculated on SiO ₂ based on the dry residue of the paper mixture, on the dehydration effect .

EXAMPLE 5
In this series of experiments, the dehydration effect is evaluated in the same way as in Example 3, except that sodium acetate is used to control the conductivity.
(550 ppm Na ⁺ ) and calcium chloride (1300 ppm Ca ²⁺ ).

 In this series of experiments, polymers and anionic mineral particles are similarly used, as in Example 1.

Table 5 presents data showing the effect of different dosages of particles based on silicon dioxide, calculated on SiO ₂ on the dry residue of the paper mixture, on the effect of dehydration.

EXAMPLE 6
In this series of experiments, the effect of dehydration and retention was evaluated in the same way as in Example 3, using a combination of sodium acetate (550 ppm Na ⁺ ) and calcium chloride (1300 ppm Ca ²⁺ ) to control the conductivity.

 In this series of experiments, the same polymers are similarly used as in Example 1. The anionic micronized material used is a hydrated suspension of powdered bentonite-Na. Bentonite has a surface charge of approximately 0.33 meq / g and a swelling capacity of 41 ml (2 g). Particles of bentonite are added in an amount of 8.0 kg / t, calculated on the dry bentonite of the dry residue of the paper mixture.

 Table 6 presents data showing the effect of different dosages of P1 and P2 calculated on the dry polymer of the dry residue of the paper mixture on the effect of dehydration.

EXAMPLE 7
In this series of experiments, the dehydration effect is evaluated in the same way as in Example 6, except that sodium chloride is used to control the conductivity.

 In these experiments, polymers and bentonite are similarly used, as in Example 6. Particles of bentonite are added in an amount of 8.0 kg / t calculated on dry bentonite of the dry residue of the paper mixture. Table 7 presents data showing the effect of various dosages P1 and P2, calculated on the dry polymer of the dry residue of the paper mixture, on the effect of dehydration and retention.

EXAMPLE 8
In this series of experiments, the dehydration effect is evaluated in the same manner as in Example 3, except that zinc chloride is used to control the conductivity. In these experiments, the same polymers and anionic mineral particles are similarly used as in Example 1.

Table 8 presents the results of experiments on dehydration at various dosages of particles based on silicon dioxide based on SiO ₂ and the dry residue of the paper mixture.

Claims (16)

 1. A method of manufacturing paper from a suspension containing cellulosic fibers and optional excipients, comprising adding dehydration and retention aids to the suspension, including a cationic organic polymer, molding and dewatering the suspension on a mesh, characterized in that the cationic organic polymer contains an aromatic group and is added in an amount of at least 0.001% based on the dry residue of the pulp, while the suspension, dehydrated on the grid, has a specific conductivity of at least 2.0 mS / cm  2. The method according to p. 1, characterized in that the suspension, dehydrated on the grid, has a specific conductivity of at least 5.0 mS / cm.  3. The method according to p. 1 or 2, characterized in that it further includes dewatering the suspension on a grid to obtain a wet paper web and white water, recycling white water and introducing fresh water to obtain a suspension containing cellulose fibers and optional fillers, the amount fresh water introduced is less than 20 tons per 1 ton of dry paper produced.  4. The method according to any one of paragraphs. 1, 2 or 3, characterized in that less than 10 tons of fresh water are introduced per 1 ton of dry paper obtained.  5. The method according to any one of the preceding paragraphs, characterized in that the cationic organic polymer is a vinyl addition polymer comprising in the polymerized form one or more monomers containing at least one monomer containing an aromatic group.  6. The method according to any one of the preceding paragraphs, characterized in that the cationic organic polymer is an acrylamide-based polymer. 7. The method according to any one of the preceding paragraphs, characterized in that the cationic organic polymer contains in a polymerized form a cationic monomer containing an aromatic group and described by the general formula (I)

where R ₁ represents hydrogen or CH ₃ ; each of the radicals R ₂ and R ₃ means an alkyl group containing from 1 to 3 carbon atoms; A ₁ represents O or NH; B ₁ represents an alkylene group containing from 2 to 4 carbon atoms, or a hydroxypropylene group; Q is benzyl and X ^{is an} anionic counterion.  8. The method according to any one of the preceding paragraphs, characterized in that the cationic organic polymer has a weight average molecular weight of not less than 1,000,000.  9. The method according to any one of the preceding paragraphs, characterized in that the cationic organic polymer is obtained from a mixture of monomers, including from 5 to 20 mol. % cationic monomer containing an aromatic group, and from 95 to 80 mol. % of other copolymerizable monomers.  10. The method according to any one of the preceding paragraphs, characterized in that the means of dehydration and retention also contains anionic mineral particles.  11. The method according to p. 10, characterized in that the anionic mineral particles are selected from particles based on silicon dioxide or bentonite.  12. The method according to p. 10 or 11, characterized in that the anionic mineral particles are selected from particles based on silicon dioxide modified with aluminum.  13. The method according to any one of the preceding paragraphs, characterized in that the means of dehydration and retention also includes a low molecular weight cationic organic polymer.  14. The method according to any one of the preceding paragraphs, characterized in that the means of dehydration and retention also includes an aluminum compound.  15. The method according to any one of the preceding paragraphs, characterized in that the suspension, which is dehydrated on a grid, has a content of bivalent and multivalent cations of not less than 200 ppm.  16. The method according to any one of the preceding paragraphs, characterized in that the suspension contains recycled fibers.

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