JP2005516135A - Paper manufacturing method - Google Patents

Abstract

【the purpose】
The present invention is a method for producing paper and paperboard, comprising preparing a suspension containing cellulose fibers and at least a sizing agent, dewatering the suspension, thereby forming a paper web, An anionic polymer having a weight average molecular weight in the range of about 6,000 to about 100,000 selected from the group consisting of a group-containing cationic vinyl addition polymer and a vinyl addition polymer and a condensation polymer. The present invention relates to a method of manufacturing paper and paperboard.

Description

  The present invention relates to a process for making paper and paperboard comprising the addition of two different polymers to an aqueous cellulose-containing suspension, one of which is an aromatic-containing cationic vinyl addition polymer and the other is An anionic polymer having a weight average molecular weight ranging from about 6,000 to about 100,000 selected from the group consisting of vinyl addition polymers and condensation polymers.

Internal sizing agents are usually added to the wet end of the papermaking process, thereby reducing the ability to adsorb liquid paper. Commonly used internal sizing agents are sizing agents based on rosin derivatives and cellulose reactive sizing agents, especially ketene dimers and acid anhydrides. Multipurpose office papers need to be fairly heavily sized to function properly in today's high speed regenerators. There are many ways to measure the contact angle of water droplets on paper when sufficiently sized, i.e. to obtain a paper with a cobb ₈₀ value of 30 or less, or when an angle greater than 80 degrees shows good sizing after 10 seconds The sizing agent is added to the suspension. However, the manufacturing cost increases in addition to the possibility of stopping at the paper mill due to operational problems.
Apart from the addition of sizing agents to the pulp suspension, dehydrating agents and retention aids are also added to the suspension. As the name implies, the latter agent promotes both dehydration and retention of the pulp suspension. According to the present invention, surprisingly, the sizing efficiency is improved by the addition of at least two different types of polymers (these polymers act simultaneously as dehydrating agents and retention aids) to the pulp suspension. I understood. Thus, by applying the method, both sizing, dehydration and retention are positively affected. The effect is also observed for suspensions with high conductivity.

  According to the present invention, a paper and paperboard manufacture comprising a specially improved sizing comprising a suspension comprising cellulose and at least a sizing agent, the suspension being dehydrated and thereby forming a paper web. A method comprising adding an anionic polymer having a weight average molecular weight in the range of about 6,000 to about 100,000 selected from the group consisting of aromatic-containing cationic vinyl addition polymers and vinyl addition polymers and condensation polymers to a suspension. It has been found that it can be obtained by a method for producing paper and paperboard, characterized by addition.

  The invention is not limited to a special type of cellulose suspension, but can be applied to cellulose suspensions containing virgin or recycled pulp and different fillers, such as calcium carbonate. The pH of the suspension can also vary from being acidic (this is the case when sizing agents derived from rosin are used) to being neutral or alkaline. When a cellulose reactive sizing agent is used, the pH of the cellulose suspension is neutral to alkaline, i.e., in the range of about 5 to about 10, which is also an inorganic filler material in the suspension. Making it possible to contain, for example, precipitated calcium carbonate and clay. The two different polymers are preferably added to a highly diluted lignocellulose-containing suspension commonly referred to as a dilute stock having a concentration of 0.1% to 3.0% by weight based on dry fiber. is there.

  Furthermore, the process does not depend on the type of sizing agent added, thus any sizing agent or mixture of sizing agents may be present in the cellulose suspension. Cellulose suspensions contain a cellulose-reactive sizing agent, usually present in an amount from 0.01% to 5% by weight, based on dry fiber, and the pH value at which the cellulose-reactive sizing agent still works properly, i.e. It preferably has a pH in the range of 5 to 10. Suitable cellulose reactive sizing agents are ketene dimers, ketene multimers, acid anhydrides, organic isocyanates, carbamoyl chloride and mixtures thereof, with ketene dimers and acid anhydrides being preferred.

  According to this method, an aromatic-containing cationic vinyl addition polymer and an anionic vinyl addition polymer having a weight average molecular weight ranging from about 6,000 to about 100,000 are added to the cellulose suspension. Usually, the cationic polymer is added to the suspension prior to the addition of the anionic polymer. Preferably, there is one or more shearing steps following the addition of the cationic polymer, added after every step where the anionic polymer provides significant shear but before the formation of the paper web.

Aromatic-containing cationic vinyl addition polymers Aromatic-containing cationic vinyl addition polymers may be linear or branched and have anionic or potentially anionic groups as long as the overall charge of the polymer is cationic. Monomers may be included. However, the cationic polymer is preferably obtained by polymerizing a reaction mixture that is substantially free of monomers having anionic groups or groups that can be made anionic in aqueous compositions. The cationic polymer may be a homopolymer or a copolymer comprising a cationic aromatic monomer, a cationic non-aromatic monomer and a nonionic monomer, the latter also being non-aromatic. Preferably, the cationic vinyl addition polymer comprises a cationic aromatic monomer selected from the group consisting of acrylamide, methacrylamide, acrylate and methacrylate, whereby said cationic monomer is directly or hydrocarbon group (these are It preferably has at least one aromatic group covalently bonded to the nitrogen atom via (which may have heteroatoms). The aromatic-containing cationic vinyl addition polymer preferably comprises aromatic acrylamide (or methacrylamide) and / or acrylate (or methacrylate) monomers, which are present in the polymer in an amount from about 2 mol% to about 97 mol%. Exists. Aromatic-containing cationic vinyl addition polymers can be cationic monomers or general formula (I):

により表される陽イオンモノマーを含むモノマー混合物を含む反応混合物を重合することにより得られることが好適である。式中、R₁はＨ又はCH₃であり、R₂及びR₃は互いに独立に水素又は１〜３個の炭素原子、通常１〜２個の炭素原子を有するアルキル基であり、A₁はＯ又はNHであり、B₁は２〜８個の炭素原子、好適には２〜４個の炭素原子を有するアルキレン基、ヒドロキシプロピレン基又はヒドロキシエチレン基であり、Ｑは芳香族基、好適にはフェニル基又は置換フェニル基を含む置換基であり、これらは通常１〜３個の炭素原子、好適には１〜２個の炭素原子を有するアルキレン基により窒素に結合でき、好ましくはＱはベンジル基（-CH₂-C₆H₅）であり、かつX^-は陰イオンの対イオン、通常塩化物イオンのようなハロゲン化物イオンである。一般式(I)により表される好適なモノマーの例として、ジアルキルアミノアルキルアクリレート（又はメタクリレート）、例えば、ジメチルアミノエチルアクリレート（又はメタクリレート）、ジエチルアミノエチルアクリレート（又はメタクリレート）及びジメチルアミノヒドロキシプロピルアクリレート（又はメタクリレート）、並びにジアルキルアミノアルキルアクリルアミド（又はメタクリルアミド）、例えば、ジメチルアミノエチルアクリルアミド（又はメタクリルアミド）、ジエチルアミノエチルアクリルアミド（又はメタクリルアミド）、ジメチルアミノプロピルアクリルアミド（又はメタクリルアミド）、及びジエチルアミノプロピルアクリルアミド（又はメタクリルアミド）を塩化ベンジルで処理することにより得られた四級モノマーが挙げられる。一般式(I)の好ましい陽イオンモノマーとして、ジメチルアミノエチルアクリレートベンジルクロリド四級塩、ジメチルアミノエチルメタクリレートベンジルクロリド四級塩及びジメチルアミノプロピルアクリルアミド（又はメタクリルアミド）ベンジルクロリド四級塩が挙げられる。

It is preferred to be obtained by polymerizing a reaction mixture comprising a monomer mixture comprising a cationic monomer represented by In the formula, R ₁ is H or CH ₃ , R ₂ and R ₃ are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, usually 1 to 2 carbon atoms, and A ₁ is O or NH, B ₁ is an alkylene, hydroxypropylene or hydroxyethylene group having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms, Q is an aromatic group, preferably Is a phenyl group or a substituent containing a substituted phenyl group, which can usually be bonded to the nitrogen by an alkylene group having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms, preferably Q is benzyl A group (—CH ₂ —C ₆ H ₅ ) and X ⁻ is a counter ion of an anion, usually a halide ion such as a chloride ion. Examples of suitable monomers represented by the general formula (I) include dialkylaminoalkyl acrylates (or methacrylates) such as dimethylaminoethyl acrylate (or methacrylate), diethylaminoethyl acrylate (or methacrylate) and dimethylaminohydroxypropyl acrylate ( Or methacrylate), and dialkylaminoalkylacrylamide (or methacrylamide), such as dimethylaminoethylacrylamide (or methacrylamide), diethylaminoethylacrylamide (or methacrylamide), dimethylaminopropylacrylamide (or methacrylamide), and diethylaminopropylacrylamide (Or methacrylamide) obtained by treating with benzyl chloride Monomer, and the like. Preferred cationic monomers of the general formula (I) include dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt and dimethylaminopropylacrylamide (or methacrylamide) benzyl chloride quaternary salt.

  The cationic vinyl addition polymer may be a homopolymer prepared from a cationic monomer having an aromatic group or a copolymer prepared from a monomer mixture comprising a cationic monomer having an aromatic group and one or more copolymerizable monomers. Good. As a suitable copolymerizable nonionic monomer, the general formula (II):

により表されるモノマーが挙げられる。式中、R₄はＨ又はCH₃であり、R₅及びR₆は夫々Ｈ又は１〜６個、好適には１〜４個、通常１〜２個の炭素原子を有する炭化水素基、好適にはアルキルであり、A₂はＯ又はNHであり、B₂は２〜８個の炭素原子、好適には２〜４個の炭素原子のアルキレン基、もしくはヒドロキシプロピレン基であり、又は、Ａ及びＢが両方ともなく、それによりＣとＮの間に単結合がある（O=C-NR₅R₆）。この型の好適な共重合性モノマーの例として、アクリルアミド（又はメタクリルアミド）；N-アルキルアクリルアミド（又はメタクリルアミド）及びN,N-ジアルキルアクリルアミド（又はメタクリルアミド）のようなアクリルアミドをベースとするモノマー、例えば、N-n-プロピルアクリルアミド、N-イソプロピルアクリルアミド（又はメタクリルアミド）、N-n-ブチルアクリルアミド（又はメタクリルアミド）、N-イソブチルアクリルアミド（又はメタクリルアミド）及びN-t-ブチルアクリルアミド（又はメタクリルアミド）；並びにジアルキルアミノアルキルアクリルアミド（又はメタクリルアミド）、例えば、ジメチルアミノエチルアクリルアミド（又はメタクリルアミド）、ジエチルアミノエチルアクリルアミド（又はメタクリルアミド）、ジメチルアミノプロピルアクリルアミド（又はメタクリルアミド）及びジエチルアミノプロピルアクリルアミド（又はメタクリルアミド）；ジアルキルアミノアルキルアクリレート（又はメタクリレート）のようなアクリレートをベースとするモノマー、例えば、ジメチルアミノエチルアクリレート（又はメタクリレート）、ジエチルアミノエチルアクリレート（又はメタクリレート）、t-ブチルアミノエチルアクリレート（又はメタクリレート）及びジメチルアミノヒドロキシプロピルアクリレート；並びにビニルアミド、例えば、N-ビニルホルムアミド及びN-ビニルアセトアミドが挙げられる。好ましい共重合性ノニオン性モノマーとして、アクリルアミド及びメタクリルアミドが挙げられ、主ポリマーはアクリルアミドをベースとするポリマーであることが好ましい。

The monomer represented by these is mentioned. Wherein R ₄ is H or CH ₃ , and R ₅ and R ₆ are each H or a hydrocarbon group having 1 to 6, preferably 1 to 4, usually 1 to 2 carbon atoms, preferably Is alkyl, A ₂ is O or NH, B ₂ is an alkylene group of ₂ to 8 carbon atoms, preferably 2 to 4 carbon atoms, or a hydroxypropylene group, or A 2 And B are both absent, so there is a single bond between C and N (O = C-NR ₅ R ₆ ). Examples of suitable copolymerizable monomers of this type include monomers based on acrylamide such as acrylamide (or methacrylamide); N-alkyl acrylamide (or methacrylamide) and N, N-dialkyl acrylamide (or methacrylamide) For example, Nn-propylacrylamide, N-isopropylacrylamide (or methacrylamide), Nn-butylacrylamide (or methacrylamide), N-isobutylacrylamide (or methacrylamide) and Nt-butylacrylamide (or methacrylamide); and dialkyl Aminoalkylacrylamide (or methacrylamide), for example, dimethylaminoethylacrylamide (or methacrylamide), diethylaminoethylacrylamide (or methacrylamide), di Monomers based on acrylates such as methylaminopropyl acrylamide (or methacrylamide) and diethylaminopropyl acrylamide (or methacrylamide); dialkylaminoalkyl acrylate (or methacrylate), such as dimethylaminoethyl acrylate (or methacrylate), diethylaminoethyl Acrylate (or methacrylate), t-butylaminoethyl acrylate (or methacrylate) and dimethylaminohydroxypropyl acrylate; and vinylamides such as N-vinylformamide and N-vinylacetamide. Preferred copolymerizable nonionic monomers include acrylamide and methacrylamide, and the main polymer is preferably an acrylamide-based polymer.

  As a suitable copolymerizable cationic monomer, the general formula (III):

により表されるモノマーが挙げられる。式中、R₇はＨ又はCH₃であり、R₈及びR₉は炭化水素基であることが好ましく、１〜３個の炭素原子を有するアルキル基であることが好適であり、R₁₀は水素又は好ましくは炭化水素基、好適には１〜８個の炭素原子、通常１〜２個の炭素原子を有するアルキル基であってもよく、A₃はＯ又はNHであり、B₃は２〜４個の炭素原子、好適には２〜４個の炭素原子のアルキレン基、又はヒドロキシプロピレン基であり、かつX^-は陰イオンの対イオン、通常メチル硫酸イオン又は塩化物イオンのようなハロゲン化物イオンである。好適な陽イオン共重合性モノマーの例として、通常HCl、H₂SO₄等のような酸、又は塩化メチル、硫酸ジメチル等のような四級化剤を使用して調製される、上記ジアルキルアミノアルキルアクリレート（又はメタクリレート）及びジアルキルアミノアルキルアクリルアミド（又はメタクリルアミド）の酸付加塩及び四級アンモニウム塩；並びにジアリルジメチルアンモニウムクロリドが挙げられる。好ましい共重合性陽イオンモノマーとして、ジメチルアミノエチルアクリレート（又はメタクリレート）メチルクロリド四級塩、ジアリルジメチルアンモニウムクロリド及びジメチルアミノプロピルアクリルアミド（又はメタクリルアミド）ベンジルクロリド四級塩が挙げられる。アクリル酸、メタクリル酸、イタコン酸、種々のスルホン化ビニル付加モノマー等のような共重合性陰イオンモノマーがまた、好ましくは、少量で使用し得る。

The monomer represented by these is mentioned. In the formula, R ₇ is H or CH ₃ , R ₈ and R ₉ are preferably hydrocarbon groups, preferably alkyl groups having 1 to 3 carbon atoms, and R ₁₀ is It may be hydrogen or preferably a hydrocarbon group, suitably an alkyl group having 1 to 8 carbon atoms, usually 1 to 2 carbon atoms, A ₃ is O or NH and B ₃ is 2 An alkylene group of ˜4 carbon atoms, preferably 2-4 carbon atoms, or a hydroxypropylene group, and X ⁻ is a halogen such as a counter ion of an anion, usually a methyl sulfate ion or a chloride ion It is a fluoride ion. Examples of suitable cationic copolymerizable monomers include the above dialkylamino, usually prepared using acids such as HCl, H ₂ SO ₄ , or quaternizing agents such as methyl chloride, dimethyl sulfate, etc. And acid addition salts and quaternary ammonium salts of alkyl acrylates (or methacrylates) and dialkylaminoalkyl acrylamides (or methacrylamides); and diallyldimethylammonium chloride. Preferred copolymerizable cationic monomers include dimethylaminoethyl acrylate (or methacrylate) methyl chloride quaternary salt, diallyldimethylammonium chloride and dimethylaminopropylacrylamide (or methacrylamide) benzyl chloride quaternary salt. Copolymerizable anionic monomers such as acrylic acid, methacrylic acid, itaconic acid, various sulfonated vinyl addition monomers and the like can also be used, preferably in small amounts.

  The cationic vinyl addition polymer is preferably 1 to 99 mol%, suitably 2 to 50 mol%, preferably 5 to 20 mol% of a cationic monomer having an aromatic group, represented by the general formula (I). , Other copolymerizable monomers (which preferably contain acrylamide or methacrylamide) can be prepared from monomer mixtures generally containing 99 to 1 mol%, suitably 98 to 50 mol%, preferably 95 to 65 mol%. The monomer mixture suitably comprises 98-50 mol%, preferably 95-80 mol% acrylamide (or methacrylamide), the balance being preferably up to 100% of the compounds of the formulas I and II. It is.

  The cationic polymer may also be a polymer that has been subjected to aromatic modification using a drug containing an aromatic group. Suitable modifiers of this type include benzyl chloride, benzyl bromide, N- (3-chloro-2-hydroxypropyl) -N-benzyl-N, N-dimethylammonium chloride, and N- (3-chloro-2 -Hydroxypropyl) pyridinium chloride. A vinyl addition polymer is mentioned as a polymer suitable for such aromatic modification. If the polymer contains a tertiary nitrogen that can be quaternized by a modifier, the use of such agents usually results in the polymer being made cationic. The polymer subjected to aromatic modification may be a cation, for example, a cation vinyl addition polymer.

  Usually, the charge density of the cationic polymer is in the range of 0.1 to 8.0 meqv per gram of dry polymer, suitably 0.2 to 4.0, preferably 0.5 to 3.0. The weight average molecular weight of the cationic polymer is usually at least about 500,000, suitably about 1,000,000 or more, preferably about 2,000,000 or more. The upper limit is not important. It may be about 30,000,000, usually 20,000,000, preferably 10,000,000.

  The cationic vinyl addition polymer is a suspension in an amount that can vary within wide limits depending on, among other things, the type of suspension, salt content, salt type, filler content, type of filler, location of addition, etc. Can be added. In general, the cationic vinyl addition polymer is added in an amount that results in better sizing, dehydration and retention than would otherwise be obtained, provided that an anionic vinyl addition polymer is added. The cationic polymer is usually added in an amount of at least 0.002% by weight, often at least 0.005% by weight, based on dry pulp, the upper limit being usually 1.0% by weight, preferably 0.5% by weight.

Anionic vinyl addition polymer In addition to the aromatic-containing cationic vinyl addition polymer, an anionic polymer having a weight average molecular weight in the range of about 6,000 to about 100,000 selected from the group consisting of vinyl addition polymers and condensation polymers is cellulose. Added to the suspension. The anionic polymer may be linear, branched or crosslinked, but is preferably substantially linear and is usually water-soluble or water-dispersible. Furthermore, the anionic polymer may be a homopolymer or a copolymer comprising at least two different types of monomers. The anionic polymer is preferably a vinyl addition polymer having a weight average molecular weight ranging from about 6,000 to about 100,000. Suitable anionic vinyl addition polymers are vinylic unsaturated monomers, preferably vinylic unsaturated aromatics, having one or more anionic groups or groups that are anionized in aqueous solution, preferably at least one sulfonate group. A polymer obtained from a reaction mixture containing a group-containing monomer. Examples of anionic groups attached to vinyl unsaturated monomers are phosphate groups, phosphonate groups, sulfate groups, sulfonic acid groups, sulfonate groups, carboxylic acid groups, carboxylate groups such as acrylic acid, methacrylic acid, ethylacrylic acid. , Crotonic acid, itaconic acid, maleic acid or their salts, alkoxide groups, maleic acid groups and phenol groups, ie hydroxy-substituted phenyl and naphthyl. Groups having an anionic charge are usually alkali metal, alkaline earth or ammonia salts. Anionic vinyl addition polymers may also contain some cationic groups, such as monomers having cationic groups, but it is preferred that only the ionic groups present in the vinyl addition polymer are anions. The anionic group is preferably bonded to an aromatic vinylic (ethylenic) unsaturated monomer such as styrene, for example styrene sulfonate. When the anionic vinyl addition polymer is a copolymer, the polymer is obtained from a reaction mixture comprising nonionic vinylic unsaturated monomers such as acrylamide, methacrylamide. The anionic vinyl addition polymer may comprise an anionic monomer comprising at least one anionic charge from about 20 mole percent to about 100 mole percent.

  Suitable anionic condensation polymers having a weight average molecular weight ranging from about 6,000 to about 100,000 are aldehydes such as formaldehyde and one or more aromatic compounds containing one or more anionic groups, and any useful for condensation polymerization. Condensates with other comonomers such as urea and melamine. Examples of suitable aromatic compounds containing anionic groups are compounds based on benzene and naphthalene containing anionic groups, such as phenolic and naphtholic compounds, such as phenol, naphthol, resorcinol and their derivatives, aromatic acids And salts thereof such as phenyl acid and its salts, phenolic acid and its salts, naphthylic acid and its salts, and naphtholic acid and its salts, usually sulfonic acids and sulfonates such as benzenesulfonic acid and benzenesulfonate, xylenesulfonic acid and Xylene sulfonate, naphthalene sulfonic acid and naphthalene sulfonate, phenol sulfonic acid and phenol sulfonate are included. Examples of suitable anionic condensation polymers include condensation polymers based on the anionic benzene and naphthalene, preferably condensation polymers based on naphthalene sulfonic acid and condensation polymers based on naphthalene sulfonate.

  The weight average molecular weight of the anionic vinyl addition polymer and the condensation polymer ranges from about 6,000 to about 100,000. The lower limit is suitably from about 7,000, preferably from about 8,000, preferably from about 1,500, preferably from about 25,000, while the upper limit is suitably up to about 80,000, preferably up to about 75,000, preferably up to 45,000. , Preferably up to about 40,000. Any combination of lower and upper limits may be a preferred range. When the anionic polymer is a vinyl addition polymer, the preferred range of weight average molecular weight is from about 10,000 to about 100,000, more preferably from about 15,000 to about 75,000, and most preferably from about 25,000 to about 45,000.

Anionic polymers may have, among other things, an anionic substitution degree (DS _A ) that varies over a wide range depending on the type of polymer used. DS _A is usually 0.01 to 2.0, preferably 0.02 to 1.8, preferably 0.025 to 1.5, and the degree of aromatic substitution (DS _Q ) is 0.001 to 1.0, usually 0.01 to 1.0, preferably 0.02 to 0.7, preferably It may be 0.025 to 0.5. When the anionic polymer contains a cationic group, the cation substitution degree (DS _C ) may be, for example, 0 to 0.2, suitably 0 to 0.1, preferably 0 to 0.05, and the anionic polymer Having an anionic charge of Usually, the anionic charge density of the anionic polymer is in the range of 0.1 to 6.0 meqv per gram of dry polymer, suitably 0.5 to 5.0, preferably 1.0 to 5.0.

  The anionic polymer is added to the suspension in an amount that can vary within wide limits depending on, among other things, the type of stock, salt content, salt type, filler content, type of filler, location of addition, etc. Can do. In general, the anionic polymer is added in an amount that provides better sizing, dehydration and retention than is obtained without the addition of the anionic polymer, provided that a cationic vinyl addition polymer is added. The anionic polymer is usually added in an amount of at least 0.001% by weight, often at least 0.005% by weight, based on dry pulp, and the upper limit is usually 3.0% by weight, preferably 1.0% by weight.

According to one preferred embodiment of the invention, the aromatic-containing cationic vinyl addition polymer preferably comprises further cationic polymers, such as synthetic cationic polymers and naturally occurring polymers, preferably aqueous compositions. It can be prepared as an aqueous solution. Suitable synthetic cationic polymers are cationic vinyl addition polymers such as acrylamide-based polymers or acrylate-based polymers. Other synthetic cationic polymers include cationic condensation polymers such as epihalohydrin polymers, for example, polymers produced by reacting aliphatic amines and epichlorohydrin, polyamidoamine polymers, and polyethyleneimine polymers. Preferred naturally occurring cationic polymers are cationic polysaccharides, especially cationic starch and aromatic substituted cationic starch. The aqueous solution preferably contains a dominant amount, i.e. at least 50% by weight of the aromatic-containing cationic vinyl addition polymer, even if the effect is present in a rather small amount reduced to an amount of at least 10% by weight. . Additional cationic polymers mentioned in this section may also be added separately.
According to yet another preferred embodiment of the invention, inorganic anionic particulate materials such as anionic silica-based particles, polysilicic acid and smectite type clays are added to the suspension. The inorganic anionic particulate material can be added separately to the suspension or is preferably included in an aqueous composition that also contains an anionic polymer.

  Furthermore, the process can also be beneficial for the production of paper and paperboard from cellulose suspensions with high conductivity. In such cases, the conductivity of the suspension to be dewatered on the wire is usually at least 1.0 mS / cm, suitably at least 2.0 mS / cm, preferably at least 3.5 mS / cm. Conductivity can be measured with conventional equipment, such as the WTW LF 539 equipment supplied by a Christian burner. The above values are supplied to the head box of the paper machine, or by measuring the conductivity of the cellulose suspension present in it, or measuring the conductivity of white water obtained by dehydrating the suspension. It is suitable to measure by doing. High conductivity level means high content of salt (electrolyte) that can be derived from the materials used to produce the stock, various additives introduced into the stock, raw water supplied to the process, etc. To do. Furthermore, the salt content is usually high in the way in which white water is circulated thoroughly, which can lead to a considerable accumulation of salt in the water circulating in the process.

  The invention is further illustrated by the following examples, which are not intended to limit the invention. Parts and% relate to parts by weight and% by weight, respectively, based on dry fiber unless otherwise stated. All ingredients added to the furnish are calculated as dry material unless otherwise indicated. In the examples, good retention is indicated by low turbidity values in white water, i.e. more fines and fillers are retained in the formed sheet. Turbidity values below 120 are acceptable, and values below 90 are excellent in this set of experiments. The dehydration number should also be low. Paper sizing was measured by the contact angle of water droplets on the paper. A contact angle greater than 80 degrees after 10 seconds indicates good sizing.

  The pulp used (in 3%) was an 80/20 mixture of hardwood / conifer craft. Ground calcium carbonate filler (GCC) was added to the pulp to a filler concentration of 40% dry solids. The resulting furnish was diluted to 0.3%, after which additional chemicals were added. Chemical addition is expressed as a percentage of the dry solids in the furnish.

  In this example, two types of furnish are used, one having a low conductivity of 500 μS / cm (finishing material I) and the other having a high conductivity of 4.0 μS / cm. (Finished Paper II). The conductivity was adjusted by adding sodium sulfate. A dispersion containing the usual ketene dimer sizing agent and 1% cationic starch was added to the furnish. Following these additions, 0.1% silica sol with 0.1% aromatic cation polyacrylamide (A-PAM) with benzyldimethylammonium groups or 0.1% normal non-aromatic cation polyacrylamide (C-PAM). Or added prior to the addition of 0.1% anionic polystyrene sulfonate (PSS) having a weight average molecular weight of 70,000. The amount of compound added is shown in Tables 1 and 2. The retention properties and dewatering properties of the finished furnish were evaluated by measuring the dewatering time using a dynamic dewatering analyzer (DDA-unit). A low value in this test means good dewatering efficiency. Retention was evaluated by measuring the turbidity of white water with a neferometer from Novacin. Low turbidity values mean high retention of solids in the DDA-unit. In addition, the sizing of generated, dried and cured paper is evaluated by measuring the contact angle of water after 10 seconds using a dynamic absorption and contact angle tester (DAT) from Fibro Systems. did. A high value of the contact angle means good sizing efficiency.

As shown by Table 1, the addition of aromatic modified cationic vinyl addition polymer and anionic vinyl addition polymer significantly increases sizing efficiency as well as dehydration and retention.
* No addition of cationic polyacrylamide or anionic compound; other conditions were the same as in Tests 1 and 2.

The furnish used was the same as that used in Example 1, but in this example the furnish was adjusted to a conductivity of 400 μS / cm.
The sizing dispersion used in Example 1 was added to the furnish, followed by the cationic starch. The dose for size was 0.03% (calculated as active ketene dimer for dry furnish) and the dose for cationic starch was 1.0%. Following these additions, an aromatic cationic polyacrylamide having 0.1% benzyldimethylammonium groups was converted to 0.07% of each of anionic polystyrene sulfonate and anionic naphthalene sulfonate having different weight average molecular weights shown in Table 3. Added before addition. The amount of compound added is shown in Table 3. The retention and dewatering properties of the finished furnish were evaluated by measuring the dewatering time using a DDA-unit. Retention was evaluated by measuring the turbidity of white water with a nepherometer 156 from Novacin. Furthermore, the sizing of the produced, dried and cured paper was evaluated by measuring the contact angle of water after 10 seconds using a DAT device.

Tests 1-5 are in accordance with the present invention, i.e., anionic polymers having a weight average molecular weight ranging from about 6,000 to about 100,000. As can be seen in Table 3, the sizing efficiency is significantly increased while at the same time the turbidity and dewatering performance is higher for tests 1-5 compared to the blank. In addition, comparing test 6 with tests 1-5 (the latter five are according to the invention), the sizing efficiency is very high and at the same time the turbidity value still shows good retention. Furthermore, the contact angle of 69.2 obtained in Test 6 is not an acceptable sizing degree. Thus, the overall performance of tests 1-5 regarding retention, dehydration and, at least, sizing is clearly superior to that of test 6.
* No addition of cationic polyacrylamide or anionic compound; other conditions were the same as in tests 1-6.

Claims (13)

  A method for producing paper and paperboard, comprising preparing a suspension comprising cellulose fibers and at least a sizing agent, dehydrating said suspension, thereby forming a paper web, wherein the suspension contains aromatics Production of paper and paperboard characterized by adding a cationic vinyl addition polymer and an anionic polymer having a weight average molecular weight in the range of about 6,000 to about 100,000 selected from the group consisting of vinyl addition polymers and condensation polymers Method.   The method of claim 1, wherein the anionic polymer has a weight average molecular weight ranging from about 6,000 to about 80,000.   The method according to claim 1, wherein the anionic polymer comprises an aromatic monomer having a sulfonate group.   2. A process according to claim 1, characterized in that the anionic polymer is selected from the group of vinyl addition polymers.   The method of claim 4, wherein the anionic vinyl addition polymer comprises an aromatic monomer.   6. A process according to claim 5, characterized in that the aromatic monomer has at least one sulfonate group.   5. A process according to claim 4, characterized in that the anionic vinyl addition polymer is polystyrene sulfonate.   8. A process according to any one of the preceding claims, characterized in that the anionic polymer is added to the suspension in an amount from about 0.005% to about 1.0% by weight, based on dry pulp.   9. A process according to any of claims 1 to 8, characterized in that the aromatic-containing cationic vinyl addition polymer has a weight average molecular weight of at least about 500,000.   The process of claim 1 wherein the cationic vinyl addition polymer is prepared from a reaction mixture comprising a cationic monomer having from about 1 mole percent to 99 mole percent aromatic groups. A cationic monomer having an aromatic group is represented by the formula (I)

Wherein R ₁ is H or CH ₃ , R ₂ and R ₃ are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, A ₁ is O or NH, and B ₁ Is an alkylene group having 2 to 8 carbon atoms, Q is a substituent containing an aromatic group, and X ⁻ is a counter ion of an anion)
The method of claim 11, wherein:   12. A process according to any one of the preceding claims, characterized in that the aromatic-containing cationic vinyl addition polymer is added in an amount from about 0.002% to about 1.0% by weight, based on dry pulp.   The method of claim 1, wherein the suspension comprising cellulose fibers has a conductivity of at least about 1.0 mS / cm.