DE69908939T2 - METHOD FOR PRODUCING PAPER - Google Patents

Abstract

The invention relates to a process for the production of paper from a suspension containing cellulosic fibres, and optional fillers, which comprises adding to the suspension a drainage and/or retention aid comprising a cationic organic polymer, forming and dewatering the suspension on a wire, wherein the cationic organic polymer has an aromatic group and the suspension which is dewatered on the wire has a conductivity of at least 2.0 mS/cm.

Description

This invention relates to the production of paper and more particularly to a method of manufacture of paper in which a cationic organic polymer containing a having aromatic residue, is added to the raw material ("stock") of papermaking. The process provides improved drainage and retention.

background

According to the state of papermaking technology is a headbox with an aqueous suspension containing Cellulose fibers and optionally fillers and additives, which is called raw material, which feeds the raw material ejected onto a forming sieve. Through the forming sieve becomes Water is separated from the raw material, leaving a wet paper web is formed on the wire and the web is in the drying area the paper machine further drained and dried. The water that is obtained by the drainage of the raw material is and as white water (circulating water, Engl. "white water ") will, contains usually fine particles, for example fine fibers, fillers and additives, and is usually in the cycle of the papermaking process recycled. Usually be drainage and retention aids introduced into the raw material to drainage facilitate and the adsorption of fine particles on the cellulose fibers to increase, so they are with the fibers retained on the sieve. As drainage and pensions are very often cationic organic Polymers, such as cationic starch and cationic acrylamide-based polymers. These polymers can Used alone, but become more common with others Polymers and / or with anionic microparticulate materials, such as with anionic inorganic particles, such as colloidal silica, colloidal aluminum modified silica and bentonite, used.

The U.S. patents with the numbers 4,980,025; 5,368,833; 5,603,805; 5,607,552 and 5,858,174, as well as the International Patent Application WO 97/18351 disclose the use of cationic and amphoteric polymers based on acrylamide and anionic inorganic particles as additives to the raw material papermaking. These additives are among the most effective drainage and retention aids that are currently used. Similar Systems are in the European Patent Application No. 805,234.

However, it was observed that the performance of the drainage and retention aids comprising cationic organic polymers, deteriorates when used in raw materials with high salt contents, the called a high electrical conductivity, and with solved and colloidal substances. In such raw materials are usually higher Dosages of the cationic polymer necessary, but usually the dewatering and retention effect is not completely satisfactory. These problems are observed in papermaking plants, in which the white water on a large scale is recycled into the circulation and in which only a small amount of fresh water in the process introduced, causing the accumulation of salts and colloidal Materials in white water and in the raw material to be drained is further increased.

The invention

According to the present invention, it has been found that in raw materials with high salt contents (with high electrical conductivity) and with colloidal materials and / or in papermaking processes with a high degree of white water closure, by the use of a drainage and retention aid comprising a cationic organic polymer having an aromatic moiety, improved drainage and retention can be obtained More specifically, the present invention relates to a process for producing paper from a cellulosic fiber and optionally a filler-containing suspension comprising Adding a dehydration and retention aid comprising a cationic organic polymer to the suspension, shaping and dewatering the suspension on a screen, the method being characterized in that the cationic organic polymer has an aromatic moiety st and that the suspension, which is dewatered on the screen, has an electrical conductivity of at least 2.0 mS / cm. The present invention also relates to a method as described in the preceding preamble, which method is further characterized by comprising shaping and dewatering the suspension on a screen to form a wet web containing cellulosic fibers or paper and obtaining white water, and that it comprises recirculating the white water and optionally introducing fresh water to produce a cellulosic fiber and optionally filler-containing suspension to be dewatered to make paper, the cationic organic polymer having a molecular weight aromatic Rest and the amount of introduced fresh water is less than 30 tons per ton of dry paper produced. The invention therefore relates to a method which is further defined in the claims.

The present invention leads to a improved drainage and / or retention, if one uses raw materials, over one high salt content, and therefore over a high level of electrical conductivity feature, and having a high content of colloidal materials. The present invention leads also to an improved drainage and / or retention, when applied to papermaking processes applies, in which large Scope white water recycled to the circuit and to a limited extent Fresh water supplied and / or when applied to processes involving fresh water is used with high salt contents, especially in salts of di- and polyvalent cations, such as calcium. The present invention allows thereby increasing the speed of the paper machine and to use lower dosages of additives, with a comparable drainage and / or retention effect is achieved and what an improved Paper production process and leads to economic benefits.

The cationic organic polymer, according to this invention, having an aromatic moiety, also referred to herein as the "main polymer", is capable of acting as a dewatering and retention aid (dewatering and retention aid). and retention aids "as used herein refers to one or more components (adjuvants, agents or adjuncts) which, when added to a feedstock, result in improved drainage and / or retention as compared to that obtained Drainage and / or retention, if one does not admit these one or more components. Accordingly, the main polymer provides improved drainage and / or retention both when used alone and when used in conjunction with one or more additional raw material additives. The main polymer may be linear, branched or crosslinked, for example in the form of a microparticulate material. It is preferred if the main polymer is water-soluble or water-dispersible. The aromatic moiety of the main polymer may be present in the polymer backbone, or it may preferably be a pendant moiety attached to or extending from the polymer backbone, or it may preferably be present in an attached moiety attached to the polymer backbone (backbone) is or extends from this. Suitable aromatic radicals (aryl radicals) include radicals which have a phenyl radical which is optionally substituted, a phenylene radical which is optionally substituted, and a naphthyl radical which is optionally substituted, for example radicals having the general formulas -C ₆ H ₅ , - C ₆ H ₄ -, -C ₆ H ₃ - and -C ₆ H ₂ -, for example in the form of a phenylene group (-C ₆ H ₄ -), a xylylene group (-CH ₂ -C ₆ H ₄ -CH ₂ -), a phenyl group (-C ₆ H ₅ ), a benzyl group (-CH ₂ -C ₆ H ₅ ), a phenethyl group (-CH ₂ CH ₂ -C ₆ H ₅ ) and a substituted phenyl (for example -C ₆ H ₄ -Y, -C ₆ H ₃ Y ₂ and -C ₆ H ₂ Y ₃ ), wherein one or more substituents (Y) attached to the phenyl ring may be selected from hydroxyl group, halogens, for example chlorine, Nitro group and hydrocarbon radicals having from 1 to 4 carbon atoms.

wobei R₁ die Bedeutung H oder CH₃ hat; R₂ und R₃ jeweils oder bevorzugt ein Alkylrest sind, welcher 1 bis 3 Kohlenstoffatome, normalerweise 1 bis 2 Kohlenstoffatome aufweist; A₁ die Bedeutung O oder NH hat; B₁ ein Alkylenrest mit 2 bis 8 Kohlenstoffatomen, geeigneterweise mit 2 bis 4 Kohlenstoffatomen, oder ein Hydroxypropylenrest ist; Q ein Substituent ist, der einen aromatischen Rest enthält, geeigneterweise einen Phenyl- oder substituierten Phenylrest, der an den Stickstoff über einen Alkylenrest, normalerweise mit 1 bis 3 Kohlenstoffatomen, geeigneterweise 1 bis 2 Kohlenstoffatomen, angefügt ist, und Q bevorzugt eine Benzylgruppe (-CH₂-C₆H₅) ist; und X^- ein anionisches Gegenion ist, normalerweise ein Halogenid, wie Chlorid. Beispiele für geeignete Monomere der allgemeinen Formel (I) schließen quartäre Monomere ein, die durch Behandlung von Dialkylaminoalkyl(meth)acrylaten, zum Beispiel Dimethylaminoethyl(meth)acrylat, Diethylaminoethyl(meth)acrylat und Dimethylaminohydroxypropyl(meth)acrylat und Dialkylaminoalkyl(meth)acrylamiden, zum Beispiel Dimethylaminoethyl(meth)acrylamid, Diethylaminoethyl(meth)acrylamid, Dimethylaminopropyl(meth)acrylamid und Diethylaminopropyl(meth)acrylamid mit Benzylchlorid erhalten werden. Bevorzugte kationische Monomere der allgemeinen Formel (I) schließen quartäres Dimethylaminoethylacrylatbenzylchloridsalz und quartäres Dimethylaminoethylmethacrylatbenzylchloridsalz ein.The main polymer may be selected from homopolymers and copolymers prepared from one or more monomers comprising at least one monomer having an aromatic group, suitably an ethylenically unsaturated monomer, and the main polymer is suitably a vinyl addition polymer. The term "vinyl addition polymer" as used herein refers to a polymer prepared by the addition polymerization of one or more vinyl monomers or ethylenically unsaturated monomers including, for example, acrylamide-based and acrylate-based monomers Suitable major polymers include cationic vinyl addition polymers obtained by polymerizing a cationic monomer or a mixture of monomers comprising a cationic monomer of the general formula (I):

wherein R _{1 is} H or CH ₃ ; R ₂ and R _{3 are} each or preferably an alkyl group having 1 to 3 carbon atoms, usually 1 to 2 carbon atoms; A _{1 is} O or NH; B _{1 is} an alkylene radical of 2 to 8 carbon atoms, suitably of 2 to 4 carbon atoms, or a hydroxypropylene radical; Q is a substituent containing an aromatic radical, suitably a phenyl or substituted phenyl radical attached to the nitrogen via an alkylene radical, usually of 1 to 3 carbon atoms, suitably 1 to 2 carbon atoms, and Q preferably a benzyl group (- CH ₂ -C ₆ H ₅ ); and X ^{- is} an anionic counterion, usually a halide, such as chloride. Examples of suitable monomers of general formula (I) include quaternary monomers obtained by treatment of dialkylaminoalkyl (meth) acrylates, for example dimethylaminoethyl (meth) acrylate, diethylamino thyl (meth) acrylate and dimethylaminohydroxypropyl (meth) acrylate and dialkylaminoalkyl (meth) acrylamides, for example, dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and diethylaminopropyl (meth) acrylamide with benzyl chloride. Preferred cationic monomers of general formula (I) include dimethylaminoethyl acrylate benzyl chloride quaternary salt and dimethylaminoethyl methacrylate benzyl chloride quaternary salt.

wobei R₄ die Bedeutung H oder CH₃ hat; R₅ und R₆ jeweils die Bedeutung H haben, oder ein Kohlenwasserstoffrest sind, geeigneterweise ein Alkylrest, welcher 1 bis 6, geeigneterweise 1 bis 4 und normalerweise 1 bis 2 Kohlenstoffatome aufweist; A₂ die Bedeutung O oder NH hat; B₂ ein Alkylenrest mit 2 bis 8 Kohlenstoffatomen, geeigneterweise mit 2 bis 4 Kohlenstoffatomen, oder ein Hydroxypropylenrest ist, oder in einer anderen Ausführungsform, bei der A und B nicht vorhanden sind, zwischen C und N eine Einfachbindung besteht (O=C-NR₅R₆). Beispiele für geeignete copolymerisierbare Monomere dieses Typs schließen (Meth)acrylamid; Monomere auf Acrylamidbasis, wie N-Alkyl(meth)acrylamide und N,N-Dialkyl(meth)acrylamide, zum Beispiel N-n-Propylacrylamid, N-Isopropyl(meth)acrylamid, N-n-Butyl(meth)acrylamid, N-Isobutyl(meth)acrylamid und N-t-Butyl(meth)acrylamid; und Dialkylaminoalkyl(meth)acrylamide, zum Beispiel Dimethylaminoethyl(meth)acrylamid, Diethylaminoethyl(meth)acrylamid, Dimethylaminopropyl(meth)acrylamid und Diethylaminopropyl(meth)acrylamid; Monomere auf Acrylatbasis, wie Dialkylaminoalkyl(meth)acrylate, zum Beispiel Dimethylaminoethyl(meth)acrylat, Diethylaminoethyl(meth)acrylat, t-Butylaminoethyl(meth)acrylat und Dimethylaminohydroxypropylacrylat; und Vinylamide, zum Beispiel N-Vinylformamid und N-Vinylacetamid ein. Bevorzugte copolymerisierbare nicht ionische Monomere schließen Acrylamid und Methacrylamid, das heißt (Meth)acrylamid, ein und das Hauptpolymer ist bevorzugt ein Polymer auf Acrylamidbasis.The main polymer may be a homopolymer prepared from a cationic monomer having an aromatic group or may be a copolymer prepared from a monomer mixture comprising a cationic monomer having an aromatic group and one or more copolymerizable monomers. Suitable copolymerizable nonionic monomers include monomers of the general formula (II):

wherein R _{4 is} H or CH ₃ ; R ₅ and R _{6 are} each H or a hydrocarbyl group, suitably an alkyl group having 1 to 6, suitably 1 to 4, and normally 1 to 2, carbon atoms; A _{2 is} O or NH; B _{2 is} an alkylene radical having 2 to 8 carbon atoms, suitably having 2 to 4 carbon atoms, or a hydroxypropylene radical, or in another embodiment where A and B are absent, there is a single 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 such as N-alkyl (meth) acrylamides and N, N-dialkyl (meth) acrylamides, for example Nn-propylacrylamide, N-isopropyl (meth) acrylamide, Nn-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 such as 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, that is, (meth) acrylamide, and the main polymer is preferably an acrylamide-based polymer.

wobei R₇ die Bedeutung H oder CH₃ hat; R₈ R₉ und Rio jeweils die Bedeutung H haben, oder bevorzugt ein Kohlenwasserstoffrest sind, geeigneterweise ein Alkylrest, welcher 1 bis 3 Kohlenstoffatome, normalerweise 1 bis 2 Kohlenstoffatome aufweist; A₃ die Bedeutung O oder NH hat; B₃ ein Alkylenrest mit 2 bis 4 Kohlenstoffatomen, geeigneterweise mit 2 bis 4 Kohlenstoffatomen, oder ein Hydroxypropylenrest ist; und X^- ein anionisches Gegenion ist, normalerweise Methylsulfat oder ein Halogenid, wie Chlorid. Beispiele für geeignete kationische copolymerisierbare Monomere schließen Säureadditionssalze und quartäre Ammoniumsalze der vorstehend erwähnten Dialkylaminoalkyl(meth)acrylate und Dialkylaminoalkyl(meth)acrylamide ein, die normalerweise unter Verwendung von Säuren, wie HCl, H₂SO₄, und so weiter, oder quartärisierenden Mitteln, wie Methylchlorid, Dimethylsulfat, und so weiter; und Diallyldimethylammoniumchlorid hergestellt werden. Bevorzugte copolymerisierbare kationische Monomere schließen quartäres Dimethylaminoethyl(meth)acrylatmethylchloridsalz und Diallyldimethylammoniumchlorid ein. Copolymerisierbare anionische Monomere, wie Acrylsäure, Methacrylsäure, verschiedene sulfonierte Vinyladditionsmonomere, und so weiter können ebenfalls, und bevorzugt in geringen Mengen, verwendet werden.Suitable copolymerizable cationic monomers include monomers of the general formula (III):

wherein R _{7 is} H or CH ₃ ; R ₈ R ₉ and R each have the meaning H, or preferably are a hydrocarbon radical, suitably an alkyl radical which has 1 to 3 carbon atoms, normally 1 to 2 carbon atoms; A _{3 is} O or NH; B _{3 is} an alkylene radical of 2 to 4 carbon atoms, suitably of 2 to 4 carbon atoms, or a hydroxypropylene radical; and X ^{- is} an anionic counterion, usually methylsulfate or a halide, such as chloride. Examples of suitable cationic copolymerizable monomers include acid addition salts and quaternary ammonium salts of the above-mentioned dialkylaminoalkyl (meth) acrylates and dialkylaminoalkyl (meth) acrylamides which are normally prepared using acids such as HCl, H ₂ SO ₄ , etc., or quaternizing agents, such as methyl chloride, dimethyl sulfate, and so on; and diallyldimethylammonium chloride. Preferred copolymerizable cationic monomers include quaternary dimethylaminoethyl (meth) acrylate methyl chloride salt and diallyldimethylammonium chloride. Copolymerizable anionic monomers such as acrylic acid, methacrylic acid, various sulfonated vinyl addition monomers, and so on can also be used, and preferably in small amounts.

The main polymer, according to this Invention, can be prepared from a monomer mixture comprising generally 1 to 99 mole%, suitably 2 to 50 mole% and preferably 5 to 20 mol% cationic monomer with an aromatic Radical, preferably of the general formula (I), and 99 to 1 mol%, suitably 98 to 50 mol%, and preferably 95 to 80 mol% of other copolymerizable Monomers, preferably acrylamide or methacrylamide ((meth) acrylamide) where the monomer mixture is suitably 98 to 50 mol% and preferably 95 to 80 mol% of (meth) acrylamide and the sum of these percentages is 100 in total.

The main polymer can also be selected from polymers which are activated by a condensation reaction tion of one or more monomers containing an aromatic radical. Examples of such monomers include toluene diisocyanates, bisphenol A, phthalic acid, phthalic anhydride, and so forth, which can be used in the production of cationic polyurethanes, cationic polyamideamines, and so on.

Alternatively, or additionally the main polymer will be a polymer undergoing aromatic modification exposed using an agent containing an aromatic moiety becomes. Suitable modifying agents of this type include benzyl chloride, Benzyl bromide, N- (3-chloro-3-hydroxypropyl) -N-benzyl-N, N-dimethylammonium chloride and N- (3-chloro-2-hydroxypropyl) pyridinium chloride on. Suitable polymers for such aromatic modification include vinyl addition polymers on. When the polymer contains a tertiary nitrogen, the can be quaternized with the modifying agent leads the Use of such agents normally causes the polymer becomes cationic. In another embodiment, the polymer, which is to be exposed to an aromatic modification, cationic for example, a cationic vinyl addition polymer.

Usually the charge density is of the main polymer in a range of 0.1 to 6.0 meq / g dry Polymer, suitably in a range of 0.2 to 4.0 and preferred in a range of 0.5 to 3.0. The weight average molecular weight the synthetic main polymer is usually at least about 500,000, suitably over about 1,000,000 and preferably about about 2,000,000. The upper limit is not critical; she can at around 50,000,000, usually at 30,000,000 and suitably at 25,000,000.

The main polymer of this invention can be present in any state of aggregation, for example in solid form, for example as a powder, in liquid Shape, for example as solutions, Emulsions, dispersions, including salt dispersions, and so on. examples for suitable major polymers for use in this invention include those Polymers disclosed in U.S. Patent Nos. 5,169,540; 5,708,071 and in the European Patent applications 183 466; 525 751 and 805 234 are described. When the main polymer is added to the raw material, it is suitable in liquid Form, for example in the form of an aqueous solution or dispersion.

The main polymer can be dehydrated to the Raw material can be given in quantities that can vary widely, below dependent on others on the nature of the raw material, the salinity, the type of salts, from the filler content, on the type of filler, from the time of the addition, and so on. In general, that will Main polymer added in an amount that gives a better Retention achieved as if you had not admitted it. The Main polymer is normally present in an amount of at least 0.001 Wt .-%, often at least 0.005 wt .-%, based on the dry Substances of the raw material, added, with the upper limit normally at 3% by weight and suitably at 1.5% by weight.

In a preferred embodiment This invention will be the main polymer in conjunction with an additional Additive for used the raw material, comprising a drainage and retention aid comprising two or more components that are normally used as drainage and retention aids. The expression "the drainage and retention aids ", as used herein refers to two or more Components (the auxiliaries, the means or the additives), which, when added to a raw material, become a better one drainage and / or retention, as if you would not admit these components. Examples of suitable Additives for the Close raw material of this type anionic microparticulate Materials, for example anionic organic particles and anionic inorganic particles, water-soluble anionic vinyl addition polymers, cationic organic polymers low molecular weight, aluminum compounds and combinations one of them. In a preferred aspect of this embodiment the main polymer is combined with an anionic microparticulate material, especially with anionic inorganic particles. In another preferred aspect of this embodiment, the main polymer becomes in connection with anionic inorganic particles and a cationic low molecular weight organic polymer used. In still In another preferred aspect of this embodiment, the main polymer becomes in conjunction with anionic inorganic particles and an aluminum compound used.

Anionic inorganic particles that may be used in accordance with the invention include silica-based anionic particles and soap-tone type clays. It is preferred if the particle size of the anionic inorganic particles is in the colloidal range. Silica-based anionic particles, that is, particles based on SiO ₂ or silica, are preferably used, and such particles are normally added in the form of aqueous colloidal dispersions, so-called sols. Examples of suitable silica-based particles include colloidal silica and various types of polysilicic acids. The silica-based sols may also be modified and may also contain other elements, for example, aluminum and / or boron, which may be present in the aqueous phase and / or in the silica-based particles. Suitable silica-based particles of this type include colloidal aluminum-modified silica and aluminum silicates. Mixtures of such suitable silica-based particles can also be used the. Drainage and retention aids comprising suitable silica-based anionic particles are disclosed in U.S. Patent Nos. 4,388,150; 4,927,498; 4,954,220; 4,961,825; 4,980,025; 5,127,994; 5,176,891; 5,368,833; 5,447,604; 5,470,435; 5,543,014; 5,571,494; 5,573,674; 5,584,966; 5,603,805; 5,688,482 and 5,707,493.

Silica-based anionic particles suitably have an average particle size of less than about 50 nm, preferably less than about 20 nm, and more preferably are in the range of about 1 to about 10 nm. As is conventional in silica chemistry, the particle size refers to the average size of the primary particles, which may be aggregated or not aggregated. The specific surface area of the silica-based particles is suitably above 50 m ² / g and preferably above 100 m ² / g. In general, the specific surface area may be up to about 1700 m ² / g, and preferably up to 1000 m ² / g. The specific surface area can be measured by titration with NaOH in a known manner as described, for example, by Sears in Analytical Chemistry, 28 (1956): 12, 1981 to 1983, and in U.S. Patent No. 5,176,891. The area thus obtained represents the average specific surface area of the particles.

In a preferred embodiment of the invention, the anionic inorganic particles are silica-based particles having a specific surface area in a range from 50 to 1000 m ² / g, preferably from 100 to 950 m ² / g. Sols of silica-based particles of this type also include modified sols such as silica-based aluminum-containing sols and silica-based boron-containing sols. Preferably, the silica-based particles are present in a sol having an S-value in a range of from 8 to 45%, preferably from 10 to 30%, and containing silica-based particles having a specific surface area in one 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, which sols may be modified with aluminum and / or boron as mentioned above. For example, the surfaces of the particles may be modified with aluminum, wherein the silicon atoms are substituted to the extent of 2 to 25%. The S value can be determined as described by Iber & Dalton in J. Phys. Chem., 60 (1956), 955-957, measured and calculated. The S value indicates the extent of aggregation or microgelation, and a low S value indicates a higher level of aggregation.

In yet another preferred embodiment of the invention, the silica-based particles are selected from polysilicic acid and modified polysilicic acid having a high specific surface area, suitably above about 1000 m ² / g. The specific surface area may range from 1,000 to 1,700 m ² / g, and preferably from 1,050 to 1,600 m ² / g. The sols of the modified silica may contain other elements, for example, aluminum and / or boron, which may be present in the aqueous phase and / or in the silica-based particles. Polysilicic acid is also referred to in the art as polymeric silicic acid, polysilicic acid microgel, polysilicate and polysilicate microgel, all of which are included in the term polysilicic acid as used herein. Aluminum-containing compounds of this type are also commonly referred to as polyaluminosilicate and polyaluminosilicate microgel, both of which are embraced by colloidal aluminum-modified silica and aluminum silicate as used herein.

Clays of the soap-clay type which can be used in the process of the invention are known in the art and include naturally occurring, synthetic and chemically treated materials. Examples of suitable soap clays include montmorillonite / bentonite, hectorite, beidelite, nontronite and saponite, preferably bentonite, and in particular a bentonite having a surface area of from 400 to 800 m ² / g after swelling. Suitable clays are disclosed in US Pat. Nos. 4,753,710; 5,071,512 and 5,607,552.

Anionic organic particles that according to the invention can be used conclude highly crosslinked anionic vinyl addition polymers, suitably Copolymers comprising an anionic monomer such as acrylic acid, methacrylic acid and sulfonated or phosphonated vinyl addition monomers, usually copolymerized with nonionic monomers, such as (meth) acrylamide, Alkyl (meth) acrylates, and so on. Helpful anionic organic Close particles also anionic condensation polymers, for example melamine-sulfonic acid sols on. water-soluble anionic vinyl addition polymers used according to the invention can, conclude Copolymers comprising an anionic monomer such as acrylic acid, methacrylic acid, and sulfonated vinyl addition monomers, usually copolymerized with nonionic monomers, such as acrylamide, alkyl acrylates, and so on, such as those mentioned in the U.S. patents No. 5,098,520 and 5,185,062.

Low molecular weight (hereinafter LMW) cationic organic polymers that can be used in accordance with the invention include those polymers commonly referred to and used as anionic trash catchers (ATC). ATC's are present in the prior art as neutralizing and / or fixing agents for adversely affecting anionic substances in the raw material and their use together with the drainage and / or pension aids often provides a further improved drainage and / or retention. The cationi The organic LMW polymer can be derived from natural or synthetic sources, and it is preferred if it is a synthetic LMW polymer. Suitable organic polymers of this type include highly charged cationic organic LMW polymers such as polyamines, polyamidoamines, polyethyleneimines, homo- and copolymers based on diallyldimethylammonium chloride, (meth) acrylamides and (meth) acrylates. Based on the molecular weight of the main polymer, the molecular weight of the cationic organic LMW polymer is preferably lower, suitably at least 2,000 and preferably at least 10,000. The upper limit of molecular weight is usually about 700,000, suitably about 500,000 and normally about 200,000.

Aluminum compounds according to the invention can be used conclude Alum, aluminates, aluminum chloride, aluminum nitrate and polyaluminium compounds, such as polyaluminum chlorides, polyaluminum sulfates, polyaluminum compounds, containing both chloride and sulfate ions, polyaluminum silicate sulfates and mixtures thereof. The polyaluminum compounds can also contain anions other than chloride ions, for example, anions of sulfuric acid, Phosphoric acid, organic acids, such as citric acid and oxalic acid.

The components of the drainage and retention aids according to the invention can in a usual Way and to be given to the raw material in any order. When drainage and retention aids which are a major polymer and a nonionic microparticulate material, in particular anionic inorganic particles, it is preferred that To give main polymer to the raw material before the microparticulate material is added, even if a reverse addition would be possible. It is more preferably, the main polymer before the shear stage, which may be selected can be from pumping, mixing, cleaning, and so on, and admit add the anionic particles after this shear stage. If a cationic organic LMW polymer or an aluminum compound are used, such components are preferred prior to introduction of the main polymer, optionally used in conjunction with a anionic microparticulate Material introduced into the raw material. In another embodiment can the cationic organic LMW polymer and the main polymer substantially be introduced simultaneously into the raw material, either individually or as a mixture, as described, for example, in U.S. Pat. 5,858,174. The cationic organic LMW polymer and the main polymer are preferred prior to the incorporation of an anionic microparticulate material introduced into the raw material.

The dewatering and retention aids according to the invention can be added to the raw material to be dewater in amounts which can vary widely, inter alia, depending on the type and number of components, on the type of raw material, on the salinity, on the Type of salts, filler content, type of filler, time of addition, extent of white water retention, and so on. In general, they are added in an amount that provides better drainage and / or retention than if they had not been added. The main polymer is normally added in an amount of at least 0.001% by weight, often at least 0.005% by weight, based on the dry matter of the raw material, the upper limit being normally 3% by weight and suitably 1.5 % By weight. Similar amounts are suitable for water-soluble anionic vinyl addition polymers, if used. When an anionic microparticulate material is used in the process, the total amount added is normally at least 0.001% by weight, often at least 0.005% by weight, based on the dry matter of the raw material, the upper limit being normally 1 , 0% by weight and suitably 0.6% by weight. When silica-based anionic particles are used, the total amount to be added is suitably in a range of 0.005 to 0.5% by weight, calculated as SiO ₂ and based on the dry matter of the raw material, preferably in a range from 0.01 to 0.2% by weight. When a cationic organic LMW polymer is used in the process, it may be added in an amount of at least 0.05% based on the dry matter of the raw material to be dehydrated. Suitably, the amount is in the range of 0.07 to 0.5%, preferably in the range of 0.1 to 0.35%. When an aluminum compound is used in the process, the total amount introduced into the raw material to be dewater depends on the type of aluminum compound used and other effects desired of it. For example, it is known in the art that aluminum compounds can be used as precipitants for rosin-based sizing agents. The total amount added is normally at least 0.05%, calculated as Al ₂ O ₃ and based on the dry matter of the raw material. Suitably, the amount is in the range of 0.5% to 3.0%, preferably in the range of 0.1 to 2.0%.

The process of this invention is preferably used in the manufacture of paper from a suspension containing cellulosic fibers and optionally fillers, that is, from a raw material having a high electrical conductivity. Normally, the electrical conductivity of the raw material dewatered on the screen is at least 2.0 mS / cm, suitably at least 3.5 mS / cm, preferably at least 5.0 mS / cm and most preferably at least 7.5 mS / cm. The electrical conductivity can measured with conventional equipment, such as the WTW LF 539 device from Christian Berner. The values referred to above are suitably determined as follows: The electric conductivity of the cellulosic suspension charged to or contained in the headbox of the paper machine is measured, or alternatively, the electrical conductivity of the paper pulp is measured White water, which is obtained by dewatering the suspension. High values of electrical conductivity mean a high content of salts (electrolytes), the various salts being based on mono-, di- and polyvalent cations, such as alkali metals, for example Na ⁺ and K ⁺ , alkaline earth metals, for example Ca ²⁺ and Mg ^{2 +} , Aluminum ions, for example Al ³⁺ , Al (OH) ²⁺ and polyaluminum ions and on mono-, di- and polyvalent anions, such as halides, for example Cl ^- , sulfates, for example SO ₄ ^2- and HSO ₄ ^- , Carbonates, for example CO ₃ ^2- and HCO ₃ ^- , silicates and organic lower acids can be based. The invention is particularly useful in the production of paper from raw materials having a high content of salts with bivalent and more valent cations and normally the content of bivalent and polyvalent cations is at least 200 ppm, suitably at least 300 ppm and preferred at least 400 ppm. The salts may be derived from the stage of raw material production, that is to say from the materials used in the production of the raw material, for example water, cellulose fibers and fillers, especially in integrated installations in which a concentrated aqueous fiber suspension from the pulp plant normally is mixed with water to produce a dilute suspension suitable for making paper in the paper making plant. The salt may also be derived from various other additives incorporated in the raw material, from fresh water added in the process, and so on. In addition, the content of the salts is usually higher in the processes in which the white water is recycled to a large extent, which can lead to a considerable accumulation of salts in the water, which is recycled in the process.

The present invention includes and paper-making processes in which white water is used extensively returned to the cycle (reused), that is with a large scope to white water retention, For example, if 0 to 30 tons of fresh water for the production of a ton of dry paper, usually less than 20, suitably less than 15, preferably less than 10 and in particular less than 5 tons of fresh water per ton of paper. The repatriation of the in the process obtained white water in the cycle suitably mixing the white water with cellulose fibers and / or optionally fillers, to prepare a suspension that is to be dewatered. Preferably comprises mixing the white water with a suspension, the cellulose fibers and optionally fillers contains before the suspension reaches the forming screen for drainage. The white water can be mixed with the suspension before, during, simultaneously with or after incorporation of the drainage and retention aid components, if such are used, and they can be mixed, before, simultaneously with or after the introduction of the main polymer. fresh water can be introduced at any stage of the process; For example it can be mixed with cellulose fibers to form a suspension and it can be made with a suspension containing cellulose fibers contains be mixed to dilute them, creating a suspension produced, which is to be dewatered, before, simultaneously with or after mixing the raw material with White water and before, while, at the same time with or after incorporation of the drainage and retention aid components, if such are used; And before, at the same time with and after the introduction of the main polymer.

Other additives used in the Paper making common are, can Naturally together with the additive (s) according to the invention such as dry strength agents, wet strength agents, optical brightening agents, dyes, sizing agents, such as sizing agents rosin-based and cellulose-reactive sizing agents, for Example ketene dimers and succinic anhydrides, and so on. The cellulosic suspension, or the raw material. can also use mineral fillers from conventional Such as kaolin, china clay, titanium dioxide, Plaster, talc and natural and synthetic calcium carbonates, such as chalk, ground Marble and felled Calcium carbonate.

The process of this invention is used to make paper. Of course, the term "paper" as used herein includes not only paper and its manufacture, but also includes other cellulosic fiber-containing sheets or web-like products, such as paperboard and paperboard, and their manufacture. The process may be used to make paper from various types of suspensions of cellulose-containing fibers and the suspensions should suitably contain at least 25% and preferably at least 50% by weight of such fibers based on the dry fabric. The suspension may be made up of fibers from a chemical pulp, such as sulfate, sulfite and organosolv pulp, from a mechanical pulp such as thermomechanical pulp, chemithermomechanical pulp, from a refining pulp and out a wood pulp both hardwood, as well as softwood, based and they can also be used again fibers, optionally from celluloses from which inks have been removed, and Gemi based on it.

The invention is also characterized by the the following examples illustrate but with which it is not intended to limit this invention. If Unless otherwise indicated, parts and% are by weight and% by weight.

Example 1 (comparison)

The performance characteristics of dewatering are with a dynamic dewatering analyzer (DDA, Dynamic Drainage Analyzer), available from Akribi, Sweden, which measures the time needed for drainage through a sieve for a certain volume of raw material is needed when removing a stopper and if you apply vacuum on the side of the screen, the side, on which the raw material is present, is opposite.

The feed used was based on 70% by weight pulp of bleached birch / pine sulfate (60/40), finished to 200 ° CSF and 30% by weight ground marble. The raw material volume was 800 ml, the consistency (consistency) 0.3% and the pH was about 8.

By the addition of sodium sulfate became the electrical conductivity of the raw material adjusted to 0.47 mS / cm. During the experiment, the Raw material in a vessel with internals stirred at a speed of 1500 rpm and the addition of the chemicals was carried out as follows: i) addition of cationic polymer to the raw material, followed by stirring for 30 seconds, ii) addition of anionic inorganic particles to the raw material, followed by stirring for 15 Seconds, iii) dewatering of the raw material, whereby automatically recorded the drainage time becomes.

The polymers used in the test series were used P1), a cationic copolymer produced by Polymerization of acrylamide (90 mol%) and acryloxyethyldimethylbenzylammonium chloride (10 mol%) was prepared and that has an average molecular weight of about 6,000,000; and P2), a cationic copolymer, by polymerization of acrylamide (90 mol%) and acryloxyethyltrimethylammonium chloride (10 mol%) was prepared and that has an average molecular weight of about 6,000,000. The polymers P1 and P2 were in water disbanded and as 0.1% aqueous Solutions used.

The anionic inorganic particles used were silica-based particles of one type as 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 area of about 900 m ² / g surface-modified with aluminum to the extent of 5%. The silica-based particles were added in an amount of 1.0 kg / ton, calculated as SiO ₂ and based on the dry raw material system.

Table 1 shows the drainage time at different dosages of P1 and P2, calculated as dry Polymer in dry raw material system.

Table 1

Example 2 (comparison)

The drainage and retention effect was prepared using DDA as used in Example 1 determined together with a turbidity meter. The retention in the first run was determined by measuring the turbidity in the Filtrate, the white water obtained by the drainage of the raw material was decided.

The feed used was based on 56% by weight peroxide-bleached TMP / SGW pulp (80/20), 14% by weight bleached birch / pine sulfate pulp (60/40), refined to 200 ° CSF and 30% Wt% China Clay. To the raw material, 40 g / l of a colloidal fraction, bleach water from a SC system, were filtered through a 5 μm sieve and concentrated with a UF filter, with a cut-off of 200,000. The raw material volume was 800 ml, the consistency was 0.14% and the pH was adjusted to 4.0 using dilute sulfuric acid. The electrical conductivity was adjusted by adding calcium chloride (60 ppm Ca ²⁺ ), magnesium sulfate (18 ppm Mg ²⁺ ) and sodium bicarbonate (134 ppm HCO ₃ ^- ).

The polymers and anionic inorganic particles of Example 1 were similarly used in this series of experiments. Two dosages of the polymers were used, 1 kg / t each and 2 kg / t, calculated as dry polymer in the dry raw material system. Table 2 shows the evaporation and retention effect at various dosages of silica-based particles, calculated as SiO ₂ and based on the dry feedstock system.

Table 2

Example 3

In this series of experiments was the drainage and retention effect according to the in Example 2 described method.

The feed used was the same as that used in Example 2. The commodity volume was 800 ml and the pH was about 7. The electrical conductivity was adjusted by the addition of calcium chloride, thus creating a very high electrolyte content and a large amount of white water residue simulated were.

The polymers and anionic inorganic Particles according to example 1 were similar those used in this series of experiments.

Table 3 shows the drainage and retention effect at various dosages of silica-based particles, calculated as SiO ₂ and based on the dry feedstock system.

Table 3

Example 4

In this series of tests, the dewatering effect was determined using a Canadian Standard Freeness Tester, which is the standard method for characterizing dewatering according to SCAN-C 21: 65. All additions of the chemicals were made in a "Britt Dynamic Drainage Jar" with closed outlet, at a stirring speed of 1,000 rpm within 45 seconds, according to the procedure of Example 1, and the raw material system was then transferred to the dewatering capability tester. Here, the smallest hole in the bottom of the dehydration tester was sealed and the time to filter 400 ml of feed through the sieve device was measured. The raw material was taken from the closed facility using waste paper. The consistency was 0.14%, the electrical conductivity 8.0 mS / cm and the pH was about 7. Table 4 shows the dewatering effect at various dosages of silica-based particles, calculated as SiO ₂ and based on the dry raw material system.

Table 4

Example 5

In this series of experiments, the dewatering effect was determined as in Example 3, except that both sodium acetate (550 ppm Na ⁺ ) and calcium chloride (1300 ppm Ca ²⁺ ) were used to adjust the electrical conductivity.

The polymers and the anionic ones inorganic particles according to Example 1 were in similar Used in this series of experiments.

Table 5 shows the dewatering effect at various dosages of silica-based particles, calculated as SiO ₂ and based on the dry feedstock system.

Table 5

Example 6

In this series of experiments, the drainage and retention effects were determined as in Example 3 using sodium acetate (550 ppm Na ⁺ , together with calcium chloride (1300 ppm Ca ²⁺ ) to adjust the electrical conductivity.

The polymers according to Example 1 were in similar Used in this series of experiments. The anionic used microparticulate Material was a hydrogenated suspension of powdered Na bentonite in water. The bentonite had a surface charge of about 0.33 meq / g and a swelling capacity of 41 ml (2 g). The bentonite particles were in an amount of 8.0 kg / ton added, calculated as dry bentonite in one dry raw material system.

Table 6 shows the drainage and retention effect at different dosages of P1 and P2, calculated as a dry polymer in a dry raw material system.

Table 6

Example 7

In this series of experiments was the dewatering effect as determined in Example 6 except, that sodium chloride to adjust the electrical conductivity has been used.

The polymers and the bentonite according to example 6 were in similar Way used in these experiments. The bentonite particles were in an amount of 8.0 kg / ton, calculated as dry bentonite in a dry raw material system, added. Table 7 shows the drainage and retention effect at different dosages of P1 and P2, calculated as a dry polymer in a dry raw material system.

Table 7

Example 8

In this series of experiments was the dewatering effect as determined in example 3 except, that zinc chloride to adjust the electrical conductivity has been used. The polymers and the anionic inorganic Particles according to example 1 were in similar Way used in these experiments.

Table 8 shows the results of the dewatering experiments at various dosages of silica-based particles, calculated as SiO ₂ and based on the dry feedstock system.

Table 8

Claims (16)

A process for producing paper from a cellulosic fiber and optionally a filler-containing suspension comprising adding a dehydrating and retention aid comprising a cationic organic polymer to the suspension, shaping and dewatering the suspension on a sieve, characterized in that the cationic organic polymer has an aromatic radical and that the suspension which is dewatered on the screen has an electrical conductivity of at least 2.0 mS / cm. Method according to claim 1, characterized in that the suspension, which on the sieve drained becomes, an electrical conductivity of at least 5.0 mS / cm. Method according to claim 1 or 2, characterized in that the method further comprises dewatering the Suspension on a sieve to a paper pulp and white water to get the return in the cycle of white water and the introduction of fresh water, suspension containing cellulose fibers and, optionally, filler, which to drain is to generate, with the amount of fresh water introduced less than 20 tons per ton of dry paper produced is. Method according to claim 1, 2 or 3, characterized in that less than 10 tons Fresh water per ton of prepared dry paper initiated becomes. Method according to one the preceding claims, characterized in that the cationic organic polymer a vinyl addition polymer which is in polymerized form or more monomers comprising at least one aromatic Comprising residual monomer. Method according to one the preceding claims, characterized in that the cationic organic polymer is an acrylamide-based polymer. Process according to any one of the preceding claims, characterized in that the cationic organic polymer in polymerised form comprises a cationic monomer having an aromatic radical of the general formula (I):

wherein R _{1 is} H or CH ₃ , R ₂ and R _{3 are} each alkyl having 1 to 3 carbon atoms, A _{1 is} O or NH, B _{1 is} alkylene of 2 to 4 carbon atoms or hydroxy propylene radical, Q is a benzyl group and X ^{- is} an anionic counterion. Method according to one the preceding claims, characterized in that the cationic organic polymer a weight average molecular weight of at least 1,000,000 having. Method according to one the preceding claims, characterized in that the cationic organic polymer from a monomer mixture comprising 5 to 20 mol% of a cationic Monomers having an aromatic radical, and 95 to 80 Mole% of another copolymerizable monomer. Method according to one the preceding claims, characterized in that the drainage and retention aid further comprises anionic inorganic particles. Method according to claim 10, characterized in that the anionic inorganic particles are selected from silica-based particles or bentonite. Method according to claim 10 or 11, characterized in that the anionic inorganic particles are selected from aluminum-modified silica-based particles. Method according to one the preceding claims, characterized in that the drainage and retention aid further comprises a low molecular weight cationic organic polymer. Method according to one the preceding claims, characterized in that the drainage and retention aid further comprising an aluminum compound. Method according to one the preceding claims, characterized in that the suspension which is on the sieve drained is, a content of bivalent and polyvalent cations of at least 200 ppm. Method according to one the preceding claims, characterized in that the suspension is reused fibers includes.