The way to obtain aqueous slurry for paper manufacturing (option) and paper

 

(57) Abstract:

The invention relates to the pulp and paper industry. A method of obtaining a water suspension for making paper containing polyelectrolyte complex comprises the preparation of an aqueous suspension of pulp fibers containing water-soluble cationic polymer and a water-soluble anionic polymer, which is able to interact in the same suspension with the formation of polyelectrolyte complex, and compound containing multivalent cation having at least a charge of +3, and forming a polyelectrolyte complex. Also we propose a method in which the aqueous suspension of fibrous cellulose pulp contains surface-active carboxyl-containing compounds and water-soluble anionic compounds. The proposed paper obtained above by means of an aqueous suspension, from which it is prepared sheets of paper and dried. The technical result is to increase the strength of the paper, the improvement of its impregnation with glue, friction coefficient and dehydration. 3 S. and 21 C. p. F.-ly, 9 PL.

The present invention relates to a method of making paper from pulp containing surface-active carboxyl-containing with whom Aceh cellulose, and the paper with improved properties made this way.

A method of manufacturing paper usually includes three main stages: 1) preparation of aqueous suspension of cellulosic fibers, commonly known as the pulp; 2) adding a hardening and/or sizing agents; 3) the manufacture of sheets and drying the fibers to give the desired pulp sheet.

Wood is the most widely used source of cellulose fibrous mass containing a mixture of compounds, known as extractable substances, which consist of a complex mixture of various rosin acids, fatty acids, fats, waxes and other low molecular weight neutral compounds. The specific composition of extractable substances varies depending on the type of wood.

In the process of production of unbleached wood pulp by any of the widely known alkaline ways free acid and esters found in extractable substances into surface-active sodium salts of fatty and resin acids. These substances are usually referred to as Soaps of tall oil. When acid and mechanical ways of turning it into pulp extracted substances is practically not subject to change, but SS="ptx2">

Fatty acids and other surface-active carboxyl-containing compounds can also get into the pulp by adding foaming, wetting agents holding means and means for the cleaning of fabrics. This add on several areas can lead to high concentrations of these substances in the pulp. Fatty acids and other surface-active carboxyl-containing compounds can also get into the pulp during the process of removing printing ink that is applied during processing of some kinds of paper printing. When these surface-active carboxyl-containing compounds are present in the stage production of paper, they will be in the liquid phase and adsorbed by the surface of the fiber in the form of free acids, sodium salts or salts of ions of bivalent metals.

It is known that Soaps of tall oil and other surface-active substances negatively affect the strength of the paper and the properties of the reinforcing additives when they are in the manufacture of paper, even when contained in such a small amount as 0.05% (Worster N.E. et al. TAPPI, 63 (11) 63 (1980), Bruun H. H. Svensk Papperstidning 78 (14) 512 (1975), Springer, A. M. et al. TAPPI Journal 69 (4) 106 (1986), Brandel J. and A. Lindheim Pulp and Paper Mag.Can. T enough to influence the properties of the reinforcing additives, such as acrylamide copolymers are the unbleached pulp.

An improved method of making paper with improved strength with the use of unbleached pulp containing soluble anionic substances, also known as anionic impurities that uses a combination of water-soluble linear cationic polymer with high molecular weight and water-soluble anionic polymer that is capable of interaction with a cationic polymer in the presence of water with the formation of polyelectrolyte complex described in U.S. patent N 5338406. However, when using some of cellulose, especially those that contain Soaps of tall oil and other surface-active substances, this method is not completely effective to obtain paper with sufficient strength.

It is well known that Soaps of tall oil and other surface-active carboxyl-containing compounds interact with polyvalent cations with the formation of Soaps of metals; see, for example, Alien L. H. TAPPI Journal 71 (1) 61 (1988) and Young S. L. and Matijevic, E. J. Colloid Interface Sci. 61 (2) 287 (1977)). The products of these reactions, especially those involving the aluminum ions, resulting from alum, found various applications in bomotti surface-active carboxyl-containing compounds in the process of manufacturing paper having a negative impact on strength properties of paper. This is especially true when these substances are added in large quantities (see Worster N.E. and other TAPPI 63 (11) 63 (1980)). That is why the paper manufacturers usually try to minimize the amount of alum that they use.

Alum are aluminum sulfate Al2(SO4)3with different amounts of hydration water. They are widely used in paper industry for fixing rosin glue, increasing dehydration, improve the conservation of properties and reduction of anionic charge. For example, alum is widely used in combination with rosin, a component of tall oil, to prepare an adhesive for paper. Aluminate rosin formed by the interaction of these two substances adsorbed on the surface of the fibers and imparts hydrophobicity. In the manufacture of paper from unbleached pulp it is typically used for these purposes when added in amounts less than 1%. Overview of the study this chemical process can be found in Davison R. W. TAPPI 47 (10) 609 (1964). Sometimes alum was recommended as an agent to control the formation of the resin (see Back E. Svensk Papperstidning 59 (9) 319 (1956) and Alien L. H. TAPPI 63 (2) 81 (1980)).

Alum is also used in combination with anionic with astout as an adjuvant to save strength along with these anionic copolymers. Alum can also be used in the manufacture of paper using cationic resins, for example as a component of the impregnating composition, fixer dyes or auxiliary means for dewatering (W. F. Reynolds in "Dry Strength Additives", TAPPI Press. Atlanta, GA, 1980. Chapter 60). For example, alum used together with some cationic hydrophobic additives to increase the strength in the dry state, described Strazdins in U.S. patent 3840489 to neutralize soluble anionic substance found in the unbleached pulp. It has been shown that this substance affects the ability of the resin to increase the strength (E. Strazdins International Seminar of Paper Mill Chemistry, Amsterdam l:26p, September 11-13, 1977).

The closest analogue of the present invention is a method of obtaining a water suspension for making paper containing polyelectrolyte complex comprising the preparation of an aqueous suspension comprising cellulosic fibers and a surface-active carboxyl-containing compounds, adding to the aqueous suspension of water-soluble anionic polymer and a water-soluble cationic polymer, which is able to interact in aqueous suspension with the formation of polyelectrolyte complex (U.S. patent 5338406).

This object is achieved by a method of obtaining a water suspension for making paper containing polyelectrolyte complex, including

a) preparation of an aqueous suspension comprising cellulosic fibers and a surface-active carboxyl-containing compounds;

b) adding to the aqueous suspension of water-soluble cationic polymer and a water-soluble anionic polymer, which is able to interact in aqueous suspension with the formation of polyelectrolyte complex, and compounds containing multivalent cation having a charge equal to at least +3;

C) the formation of polyelectrolyte complex, in which the indicated compound containing a polyvalent cation, add in the concentration, which provides the number of cation equivalent on a molar basis, the amount of aluminum contained in the alum added at a concentration of from about 1.5% to about 6% (based on dry weight of cellulosic fibers.

According to a preferred variant implementation of the invention the aqueous suspension of cellulose fibres, containing surface-active carboxyl-containing compounds, also contains water-soluble anionic polymer capable vzaimodeistviya task is also achieved by a method of obtaining the aqueous slurry for the manufacture of paper, containing polyelectrolyte complex, including

a) preparation of an aqueous suspension comprising cellulosic fibres, surface-active carboxyl-containing compounds and water-soluble anionic polymer;

b) adding to the aqueous suspension of water-soluble cationic polymer that is capable of interacting with anionic polymer in aqueous suspension with the formation of polyelectrolyte complex, and compounds containing multivalent cation having a charge equal to at least +3;

C) the formation of polyelectrolyte complex, in which the indicated compound containing a polyvalent cation, add in the concentration, which provides the number of cation equivalent on a molar basis, the amount of aluminum contained in the alum added at a concentration of from about 1.5% to about 6% (based on dry weight of cellulosic fibers.

According to a preferred variant in any of the ways cationic polymer is a linear polymer.

Preferably the water-soluble cationic polymer is characterized by the results of the specific viscosity (0,05% by weight solution in 2M aqueous solution of NaCl at 30oC) greater than 2 DL/g, and PLO is the poison of less than about 5 mEq/g

The invention also refers to paper made from the aqueous suspension obtained by any of the methods mentioned above, with the subsequent production of the specified suspension of leaves and drying to obtain a paper with high strength.

The method in accordance with this invention are especially suitable in the manufacture of cardboard and corrugated facing plates with high compressive strength at higher performance. It also leads to improvement in other mechanical properties such as ultimate tensile strength, breaking strength, breaking elongation and the inner power of binding and absorption strength energy, and can be used for making paper with improved strength of the cellulose-containing surface-active carboxyl-containing compounds, in the case where it is possible to admit the desired quantity of alum.

The first stage of implementation of the method according to this invention is the obtaining of aqueous suspensions of pulp fibers by conventional methods, such as the well-known mechanical, chemical and Poluchenie methods of obtaining pulp. After mechanical grinding and/or stage chemical receiving pulp Poti stages are well known, for instance described in Casey, Pulp and Paper (New York, Interscience Publishers, Inc. 1952).

The amount of surface-active carboxyl-containing compounds present in the liquid phase, can be determined by simple extraction with ether followed by titration with base, which is a modification of standard techniques used to determine the Soaps of tall oil in the black liquor. If you do not know the exact chemical composition of the extract, this technique can only afford to calculate the weight of the present surface-active carboxyl-containing compounds. It is possible to carry out the extraction of samples of the entire pulp, in order to determine the amount of these compounds.

It is well known that soap of tall oil are present in many kinds of unbleached pulp (Drew, J. Chem.Eng.Prog. 72 (6): 64 (1976)). Lower concentrations of these substances in bleached pulp mass is primarily due to the additional steps of washing, used in the bleaching process. The amount of surface-active carboxyl-containing compounds in bleached pulp is very small, less than approximately 0.05% by weight based on the weight of dry fiber. The number of surface-active carboxyl-containing compounds in the unbleached pulp to which ocess according to this invention in the aqueous suspension of cellulose fibers are introduced water-soluble cationic polymer and a water-soluble anionic polymer, which is capable of reaction with the formation of polyelectrolyte complex and polyvalent cation having a charge equal to at least +3. Polyvalent cation added before the introduction of the water-soluble anionic polymer.

Can be used in the following order of addition: 1) a compound containing a polyvalent cation, 2) a cationic polymer, and (3) anionic polymer.

Water-soluble cationic and anionic polymers which are preferred in the practice of this invention, described in the mentioned U.S. patent N 5338406 and in European patent application 89118245.3.

The use of such cationic and anionic polymers, the term "water-soluble" means that the polymers can form necology 1% aqueous solution. Applied to cationic polymers, the term "linear" means that the polymers are linear-chain, without significant ramifications. Examples of such polymers are described below.

The charge density of the polymer can be determined based on the known structure of the polymer by the following calculation:

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It can also be determined empirically, for example, using the technique of titration colloids described L. K. Wang and W. W. Schuster in Ind. Eng. Scost (per) polymers, measured at 30oC to 2M NaCl solution containing 0.05 wt.% the polymer. Under these conditions, the cationic copolymer of acrylamide with a molecular mass of 1106characterized by the per, equal to about 2 DL/g

Cationic polymers of the present invention are water-soluble high molecular weight polymers of Quaternary ammonium compounds with a low charge density. Preferred are linear polymers. Cationic polymers have a per greater than 2 DL/g, preferably it ranges from about 7 to about 25 DL/g. They have a charge density in the range of from about 0.2 to about 4 mEq/g, preferably from about 0.5 to about 1.5 mEq/g Optimum properties are obtained from cationic polymers having a charge density of about 0.8 mEq/g Examples of cationic polymers include polysaccharides such as cationic guar (i.e., guar, modified by treatment with glycidylmethacrylate) and other derivatives of natural resins and synthetic polymers, for example copolymers of acrylamide. The latter include copolymers of acrylamide with diallyldimethylammoniumchloride (DADMAC), acryloyldimethyltaurate, methacryloyloxy-titrimetry what ammoniacloridegas. Preferred copolymers of acrylamide with DADMAC or MTMF.

Some of the cationic polymers described above may be subjected to hydrolysis of ester linkages in the conditions of high temperature, extreme pH values or long-term storage. This hydrolysis leads to the loss of cationic charge and the introduction of anionic sites in the polymer. If hydrolysis occurs to a significant extent, the polymer solution may become cloudy. However, it was found that hydrolysis does not have a significant impact on the properties of the polymer as long as the total density of cationic charges (sum of the charge density of the cationic polymer (mEq +/g) and the charge density of the anionic polymer (mEq/g)) remains in the specified interval.

The number of added cationic polymer may be in the range between about 0.1 and about 5% based on the weight of dry cellulose. The preferred amount is between about 0.2 and about 3.0 percent, and the most preferred amount is in the range from about 0.3 to about 1% based on the weight of dry pulp.

Anionic components of the present invention include those which typically contain unbleached cellulae to give the anionic nature of the natural polymers (i.e., polymers other than lignin and hemicellulose). When they are present in large quantities in the paper manufacturing process, the preferred anionic polymers, usually contained in the unbleached pulp. Preferably, anionic polymers had a charge density of less than 5 mEq/g Important class of anionic polymers of the present invention comprise water-soluble anionic polymers, which are usually located in unbleached cellulose selected from the group consisting of solubilizing lignins and hemicelluloses, sulfonated lignins, oxidized lignin, Kraft lignin and lignosulfonates. These polymers may be present in the pulp or can be added during the implementation process.

Solubilization lignins and hemicelluloses are usually contained in the unbleached pulp as a result of incomplete removal of substances, solubilizing in the process of making pulp. Such substances are formed as by chemical and mechanical obtaining pulp. Usually liquors are generated upon receipt of the pulp, such as Kraft black liquor or neutral sulfite black liquor, containing the solubilized lignin and hemicellulose.

The number of these ristomatti on the type of cellulose. The amount needed to achieve the desired increase strength in the dry state, depends on the type and amount of cationic polymer added to the pulp, the type and amount of anionic polymer contained in the pulp, the type and amount of anionic polymer added to the slurry, the amount of alum added to the slurry and applied to the sequence of the addition.

The number of added anionic polymer can range between about 0.1 and about 25%. More preferably the amount of added anionic polymer may vary between about 0.2 and about 5%. Most preferably, the amount of added anionic polymer was between about 0.25 and about 2.5%.

For a given amount of added cationic polymer magnitude increase strength increases with the amount of anionic polymer until it reaches or constant value, or maximum. This point is usually reached when a maximum number of polyelectrolyte complex. The maximum number of polyelectrolyte complex is formed approximately at the point where each charge on the cationic polymer has one anionic mo is in a dry condition, can be replaced by a water-soluble anionic polymers, usually contained in the unbleached pulp. Examples of synthetic anionic polymers and natural polymers, modified to impart anionic nature, include copolymers of acrylamide and sodium acrylate, sodium methacrylate, and 2-acrylamide-2-methyl propane sulfate sodium; sodium carboxymethyl cellulose; carboxymethylstarch sodium, sodium alginate, polypocket sodium and poly(2-acrylamide-2-methylpropanesulfonate) of sodium. They can be used individually or in any combination.

Modified to give the anionic nature of the form of lignin and hemicelluloses, such as obtained, for example, oxidation, sulfonation or carboxyethylgermanium, are also suitable. Oxidized and sulfonated lignins and hemicelluloses are byproducts of the process of transformation in the pulp and is usually contained in the unbleached cellulose used according to this invention. Contained natural lignins and hemicellulose can also be modified conventional synthesis methods, for example by oxidation, sulfonation and carboxyethylgermanium.

Polyvalent cation with at what she made of aluminum, iron, chromium, indium, rhodium, yttrium, lanthanum, cerium and praseodymium. Most preferred is aluminum, in particular aluminum, injected with alum.

The preferred number of compounds containing polyvalent cation depends on the total amount of surface-active carboxyl-containing compounds. As the total number of surface-active carboxyl-containing compounds cannot be exactly determined, it is best to determine the necessary number of connection experienced by by making small leaves with different amounts of compounds containing polyvalent cation.

When the compound containing a polyvalent cation, is an alum, the preferred amount of alum depends on the source and type of anionic polymer. When used anionic polymer is an anionic polymer contained in the cellulose, the preferred amount of alum is from about 0.4 to about 6% based on the weight of dry cellulose. The preferred amount of alum is from about 0.4 to about 4% and the most preferred amount is from about 0.4 to about 2.5%.

When the anionic polymer prego nature, the preferred amount of alum is from about 1 to about 6% based on the weight of dry cellulose. The preferred amount of alum is from about 1.25 to about 4% and the most preferred amount is from about 1.5 to about 2.5%.

If a compound containing a polyvalent cation, not an alum, the preferred number of compounds containing polyvalent cation is such that it provided a number of cation equivalent on a molar basis, the amount of aluminum, provide the specified quantity of alum.

Alum can be added at a pH of 5.5 to 11 without reducing their effectiveness in the method according to this invention. Alum, cationic polymer and anionic polymer can be added at any pH in the range of from about 4 to about 12.5. Usually the pH at points where added these Vesela in the paper manufacturing process, are between 5 and 11. Adding alum usually reduces the pH in the paper manufacturing process. Therefore, it may be necessary to add sodium hydroxide or other base to maintain the pH of the paper manufacturing process in a desirable range of 4.5 to 8.5. This can be done at any point is onenew is: alum, cationic polymer and then anionic polymer. If the preferred sequence of addition of the three components unsuitable for specific industrial applications, according to this invention can be applied to other sequences. However, the sequence of addition can adversely affect the resulting value increase strength. Individual components and mixtures of components can be dry or they may be in aqueous systems. Further, this stage can be done by obtaining the water system containing polyelectrolyte complex or a polymer, or polymers, and add the same system for the manufacture of paper.

It may also be desirable to mix the alum and cationic polymer together before adding to the system of making paper. Although there may be some reduction in the efficacy of the additive result of this mixing, the resulting lower viscosity of the polymer solution greatly facilitates the handling of the substances.

The third stage of the method according to this invention is the formation of the polyelectrolyte complex. Polyelectrolyte complex, which is formed from a mixture of cationic and anionic polymers can be in order to be called a "solution", "suspension" or "dispersion" and so on, Therefore, to avoid ambiguity, to denote such mixtures will use the General term "water system". In some cases, the term "water system" is also used for aqueous mixtures of water-soluble polymers, which form a polyelectrolyte complex.

Polyelectrolyte complex is formed when the components are mixed in an aqueous system, preferably under conditions of high shear. You can get it first and then add in the paper manufacturing process, or it can get in the paper manufacturing process. In the latter case, the cationic component may be added as such to interact with anionic polymers of natural origin or can be added simultaneously with the introduction of the anionic component or after him. In this case, the amount of each anionic polymer, which should be entered in the polyelectrolyte complex is reduced taking into account the amount of the polymer contained in the system.

The specific number and type of polyelectrolyte complex, which is preferred will depend among other factors on the characteristics of the pulp; the presence or for the formation of the complex; characteristics of the complex; the desirability of transportation on water systems containing a polyelectrolyte complex, and the nature of the process of making paper, which should be applied in the water system.

Polyelectrolyte complex usually contains polymers with cationic polymer(s) to the anionic polymer(s) is from about 1:25 to about 40: 1, preferably from about 1:4 to about 4:1. The water system is formed to be added to the pulp, usually contain 0.1 to 10 wt.% polyelectrolyte complex based on the weight of water in the system. Usually polyelectrolyte complex is effective when added to the feedstock in an amount of from about 0.1 to about 15%, preferably from about 0.2 to about 3% based on the weight of dry pulp.

The proportion of anionic charge is an indicator of the nature of the polyelectrolyte complex. It can be defined by the following formula:

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in which the total anionic charge is determined by multiplying the absolute value of the charge density (electrostatic charge per unit weight of polymer, for example in mEq/g) of each of the anionic polymer, forming a polyelectrolyte complex, the value of weight of this polymer in polyleader by multiplying the density of charge of each cationic polymer, forming a polyelectrolyte complex, the value of weight of this polymer in polyelectrolyte complex and the addition of the total amount of charge of all the cationic polymers.

Usually polyelectrolyte complex is completely dissolved when the value of the share of anionic charge less than approximately 0.2, forms a colloidal solution when the value of the share of anionic charge from about 0.2 to about 0.4 and is fibrous (in some cases in the form of a viscous gel which is deposited from a solution, but forms a colloidal solution in a high shear) when the value of the share of anionic charge in excess of about 0.4. Polyelectrolyte complexes according to this invention are usually characterized by the value of the share of anionic charge from about 0.1 to about 0,98, preferably, the value of the share anionic charge is from about 0.3 to about 0.8, and more preferably from about 0.45 to about 0.6. All of polyelectrolyte complexes according to this invention provide increased strength in the dry state, in particular in the presence of black liquor.

However, except as described below fibrous polyelectrolyte complexes (especially those that are characterized by more prasham condition, than colloidal and soluble polyelectrolyte complexes obtained from the same polymer. Under conditions of high shear in the manufacture of paper these fibrous particles dissolved with the formation of colloidal particles, which provide excellent strength properties in the dry state. Unique properties are achieved with the formation of polyelectrolyte complex by mixing anionic and cationic components in the aqueous system at a temperature equal to at least approximately 75oC, and cooling the mixture to a temperature below about 60oC, preferably below about 50oC. This can be achieved by adding dry powdered polymers in water heated at least up to 75oC, and then extracts obtained water systems for cooling to a temperature below about 60oC. Preliminary mixing of polymers with a mixture of dry polymers can facilitate the process.

The same properties can be achieved by making certain water systems anionic and cationic polymers, heating each of the water system at least up to 75oC, mixing of these systems and subsequent extracts obtained water system is today, usually characterized by the value of the share of anionic charge from about 0.1 to about to 0.98, preferably from about 0.4 to about 0.9, and most preferably from about 0.65 to about 0,85. Mixing under high shear facilitates rapid preparation of these polyelectrolyte complexes, but this is not necessary. The temperature of the solution, dispersion or suspension above about 75oC for about one hour to facilitate the homogenization of the mixture. Polyelectrolyte complexes, with a share of anionic charge less than approximately 0.2, prepared by heating at least up to 75oC and cooling will be water-soluble, and their behavior will be the same as in complexes with the same value of the share of anionic charge obtained at lower temperatures. Polyelectrolyte complexes with a value share of anionic charge equal to from about 0.2 to less than about 0,65 form colloidal particles, which behave the same way and fibrous colloidal particles, obtained without heating until at least 75oC and cooling.

When the value of the share anionic charge approximately equal to 0.65 or greater and polyelectrolyte complexes wearable is polyelectrolyte complexes, which act as additives which increase the strength in a dry condition, even better than other types of complexes according to the present invention. These soluble polyelectrolyte complexes are also suitable as activated in conditions shift flocculants, means for maintaining properties on high-speed paper machines, viscosity modifier and agents that reduce pollution, as well as in water treatment.

Water-soluble complexes can be obtained from all the above types of anionic components. However, in the paper manufacturing process temperatures are typically not high enough for the formation of such water-soluble polyelectrolyte complex. Therefore, to use those anionic polymers are generally provided in the unbleached pulp, it is necessary to separate anionic component from the pulp. This separation is usually carried out in the paper manufacturing process that makes such anionic components readily available.

Water-soluble polyelectrolyte complexes can be obtained, for example, poly(acrylamide-co-dimethylammoniumchloride) and ligninsulfonate sodium Marasperse N-3 (Lignotech USA Inc., Greenwich, CT), or Right is consistent Quaternary amine, and sodium lignosulphonate Marasperse N-22 (Lignotech USA Inc., Greenwich, CT), poly(acrylamide-co-methylacetanilide) and ligninsulfonate sodium Marasperse N-3 and poly(acrylamide-co-methylacetanilide) and ligninsulfonate sodium Marasperse N-3. However, some combinations of cationic and anionic components treated in this way, produce polyelectrolyte complexes with the largest share of anionic charge of 0.65 or higher, which form particles or colloidal particles and behave the same as their counterparts, which are formed without heating until at least 75oC and cooling.

In the implementation in practice of the present invention can also use other additives used in the paper manufacturing process. These additives may include resins that increase the strength in the wet state, adhesive, fillers, agents that reduce foaming, means for storing properties, optical brighteners, wetting agents, biocides, cleaning felt, and grids, acids, inorganic salts and bases.

The specific mechanism of the phenomenon of increasing the strength in this invention is not fully understood. The following komozi contain two types of substances, which affect the properties of chemical additives to increase the strength: 1) anionic polyelectrolytes and 2) surface-active compounds. In the above-mentioned U.S. patent N 5338406 describes how to resolve the negative impact of anionic polyelectrolytes. The present invention is aimed at overcoming the negative impact of a large number of compounds belonging to the second class, in particular surface-active compounds containing carboxyl groups.

Believe that surface-active compounds affect the manifestation of the strength of the paper by two mechanisms: 1) reduce the surface tension, which reduces the strength of the solidification, which is manifested as the paper dries, and/or 2) contribute to the formation of unstable boundary layer between the connecting fibers in the adsorption of low-melting (viscous, mechanically fragile and has low strength) compounds on the surface of the fibers.

Adding alum in a system for making paper containing these surface-active carboxyl-containing compounds leads to the formation of insoluble high-melting salts. Due to the fact that these salts are insoluble, they are no longer reduce poueu unstable boundary layer on the surface of the fibers. As a result of chemical additive to increase the strength, formed by the interaction between anionic and cationic polymers capable of acting effectively.

Therefore, the present invention provides a method for increasing the strength of paper made from pulp containing soluble polyanionic substances and/or surface-active carboxyl-containing compounds. In addition to improving strength, it has been found that the present invention: 1) allows to improve the impregnation of paper with glue during the process of making paper at a pH below 7; 2) allows to increase the coefficient of friction of paper; and 3) allows to improve the dewatering of the pulp for making paper.

The main expected benefit of this invention is in the manufacture of cardboard and corrugated blanks with high compressive strength. The invention is particularly suitable for manufacturers of these products, allowing you to get the products with excellent properties with high performance.

The following examples are given to illustrate the invention. Used the following methods.

The molecular weight of the polymer expressed in the form given specific WASC is a copolymer of acrylamide with a molecular mass of 1106has the per equal to about 2 DL/g

The content of the Soaps of tall oil (MTM) in the fibrous mass is determined by the method according to TAPPI T645 Om-89, Analysis of tall oil skimmings, and taken from "Determination of tall oil soap in black liquor" in Tall Oil, J. Drew and M. Propst, Pulp Chemicals Assn., New York, 1981. The sample filtrate fibrous masses get at pH 9, pH is brought to 2 and then conduct thorough extraction with diethyl ether. Tall oil found in diethyl ether, is determined by titration using methanolic KOH in isopropanol.

Examples 1-5.

These examples illustrate the improvement of the strength achieved in the formation of polyelectrolyte complex in the presence of alum by adding a cationic polymer and an additional amount of the solid residue from the black liquor to the unbleached pulp mass, containing black liquor and soap of tall oil.

Small leaves were produced on the leaf machine Noble and Wood (Noble and Wood Machine Co., Hoosick Falls, NY) using the following raw materials.

1. Pulp: unbleached Kraft pulp southern rocks containing 0.4% Soaps of tall oil and black liquor, as evidenced by the presence of charge soluble polyanionic equal to 0.45 mkaku/g, at pH 9, crushed the, having an alkalinity of 50 ppm million and hardness 100 ppm million, was prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 with N2SO4.

3. The agent that reduces the foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Black liquor (Jefferson Smurfit Corporation): total content of the solid residue 40,5% (according to TAPPI Standard T650).

Lignin: 11,9% (UV spectroscopy).

The charge density (colloidal titration): 0,111 mEq/g at pH 9.

3920 ml sample containing 2.5 wt.% raw materials from well-mixed portion of the crushed pulp is placed in a metal container with a volume of 4 liters In a vessel add the agent that reduces the foaming (0.025% of the weight of dry cellulose) and begin mixing. Raw materials move in the equalizing tank and diluted with up to 18 l standard hard water, described above, with a pH of 5.5. Then initial raw material, add alum, cationic copolymer (specified in the table. 1) and black liquor in quantities, the combination and sequence listed in table. 1, pH sanasto hydrated sorting sieve placed on outdoor Dekel. Dekel close and then fill in standard hard water with a pH of 5.5 (described above) from the collector to the circulating water to the bottom mark on Detelina mailbox. Extract aliquot quantity of feedstock volume of 1 liter and pour in Dekel. Mix in Dekel mix with three quick blows beat, hit delete and Dekel placed in the collection with circulating water. Tammy and detained pulp mass is then moved to open the cloth at the entrance to the press. Sheets of cloth is passed through the press with press plates, so adjusted as to obtain a pressed sheet containing 33-34% solids. Then the sheet and the sieve is placed in a drying cylinder, in which the temperature is equal to 116oC, and twice passed them at the time of transmission 50-55 (during the first cycle of the sheet is in contact with the cylinder, and during the second cycle, the sieve is in contact with the cylinder). Leaves incubated at 22oC and 50% relative humidity for 24 hours So make eight leaves, five of the last of leaves are used for testing.

Leaves appreciate if the following test: STFI Compression: TAPPI Standard T826 ("Short Span Compressive Strength of Paperboard (compressive strength bookbinding paper)).

compression - STFI Compression Strength - get when alum, cationic polymer according to this invention and the black liquor is added to industrial unbleached Kraft pulp mass containing Soaps of tall oil and having charge of the soluble polyanionic polymer.

The best indicators of the strength of the compression - STFI Compression Strength - get for samples containing alum, cationic polymer, and black liquor. Adding either some alum (example 2), alum and cationic polymer (example 3), or cationic polymer, and black liquor (example 4) results in a significantly smaller increase in strength than in the case of the use of a combination of alum, cationic polymer, and black liquor (example 5).

Examples 6-13.

These examples show the effect of sequence added to increase strength, achieved according to the invention. The leaves were made by car Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) in accordance with the procedure of examples 1-5 with the following changes.

1. Pulp: for these experiments using six different masses. The fibrous mass And raw unbleached Kraft pulp from wood southern soft rock, Jefferson-Smurfit/CCA, Fernandina, Florida.

2. Fibrous mass B: raw unbleached is th unbleached Kraft pulp from wood Western softwoods, Willamette Industries, Albany, Oregon.

Fibrous mass G: shredded corrugated containers, Willamette Industries, Albany, Oregon

Fibrous mass D: shredded corrugated containers, Willamette Industries, Port Hueneme, California.

Fibrous mass E: shredded corrugated containers, Menominee Paper Company, Menominee, Michigan.

2. Standard hard water: standard hard water with an alkalinity of 50 frequent. /m and a hardness of 100 ppm million was prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4.

3. The agent that reduces the foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)3N2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8.mol.% acrylamide, with the per 12,2 DL/g

6. Black liquor (Jefferson Smurfit Corporation): total solids content of 40.5% (according to TAPPI Standard T650).

Lignin: 11,9% (UV spectroscopy).

The charge density (colloidal titration): 0,111 mEq/g at pH of 9.0.

Each sequence is added, shown in the table. 2, carry out at least 6 times with a number of the above-mentioned fibrous masses. The data given in t which have the sequence of adding a cationic polymer, anionic polymer and alum has a significant impact on the achieved increase in strength. The biggest improvement is obtained when the following sequence: 1) alum, 2) a cationic polymer, 3) anionic polymer. Although this sequence of addition is preferred, the increase in strength is also achieved with other sequences added.

Examples 14-19.

These examples show the effect of alum on the value of increasing the strength. The leaves produced on the machine Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) according to the procedure of examples 1-5 with the following changes.

1. Fibrous mass: unbleached Kraft pulp from wood South rocks containing 0.4% Soaps of tall oil and black liquor, as evidenced by the presence of charge soluble polyanionic equal to 0.45 mkaku/g, at pH 9, crushed to the consistency of grind 678 Canadian Standard Freeness (CSF) at pH 8.

2. Standard hard water: standard hard water having an alkalinity of 50 ppm million, and hardness 100 ppm million, was prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4aluminum Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Black liquor (Jefferson Smurfit Corporation): total solids content of 40.5% (according to TAPPI Standard T650).

Lignin: 11,9% (UV spectroscopy).

The charge density (colloidal titration): 0,111 mEq/g at pH of 9.0.

The results are shown in table. 3. The increase in the number of alum leads to increase in value increase strength. How to prevent the negative impact Soaps of tall oil, found in the fibrous mass, add a sufficient quantity of alum, further enhancing the strength is not observed.

Examples 20-24.

These examples show that instead of the black liquor used in the previous examples, can be used lignosulfonate. The leaves were made by car Noble and Wood Sheet (Noble and Wood Machine Co., Hoosick Falls, NY) in accordance with the procedure of examples 1-5 with the following changes.

1. Fibrous mass: unbleached Kraft pulp mass South of the rocks containing 0,47% Soaps of tall oil and black liquor, as evidenced by the presence of charge soluble polyanionic the percentage of hard water: standard hard water with an alkalinity of 50 frequent. /m and a hardness of 100 ppm million obtained by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4.

3. Agent, a reducing foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Black liquor (Jefferson Smurfit Corporation): total solids content of 40.5% (according to TAPPI Standard T650).

Lignin: 11,9% (UV sectretary).

The charge density (colloidal titration): 0,111 mEq/g at pH of 9.0.

7. Lignosulfonate A: D-419-5, Lignotech USA. Lignosulfonate calcium.

8. Lignosulfonate B: D-419-6, Lignotech USA. Sodium lignosulphonate.

9. Lignosulfonate In: Norlig A, Lignotech USA. Lignosulfonate calcium.

The results are shown in table. 4. Comparing the examples that used a lignosulfonate, an example in which used black liquor, you can see that we have almost the same results.

Examples 25-33.

These examples show the use of this invention in the manufacture of paper d Machine Co., Hoosick Falls, NY) in accordance with the procedure of examples 1-5 with the following changes.

1. Cellulose: a return to the cycle of the pulp of corrugated containers, containing about 0.75% of a soap of tall oil and black liquor, as evidenced by the presence of charge soluble polyanionic equal to 0.01 mkaku/g, at pH of 9.0 crushed to the consistency of grind 566 Standard Freeness (CSF) at pH 8.

2. Standard hard water: standard hard water with an alkalinity of 50 ppm million and hardness 100 ppm million prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4.

3. Agent, a reducing foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)3N2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Lignosulfonate: D-419-5, Lignotech USA. Lignosulfonate calcium.

The results are shown in table. 5. When using secondary fiber pulp obtained the same value of the strength, as in the case previously achieved when the primary use of unbleached Kraft pulp. In addition, when d is show the effectiveness of this invention in the normal range of pH in the manufacture of paper. The leaves were made by car Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) in accordance with the procedure of examples 1-5 with the following changes.

1. Cellulose: a return to the cycle of the pulp of corrugated containers, containing 1.5% of a soap of tall oil and black liquor, as evidenced by the presence of charge soluble polyanionic, to 0.07 of mgecw, at a pH of 9.0 crushed to the consistency of grind 525 Canadian Standard Freeness (CSF) at pH 7.5.

2. Standard hard water: standard hard water with an alkalinity of 50 ppm million and hardness 100 ppm million prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4or NaOH depending on what is required.

3. Agent, a reducing foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Lignosulfonate: D-419-5, Lignotech USA. Lignosulfonate calcium.

The results are shown in table. 6. A three-component system, alum/polymer/black liquor has a considerable advantage in S="ptx2">

These examples show that alum and cationic polymer can be mixed before adding to the system for making paper with almost the same results. The leaves were made by car Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) according to the procedure of examples 1-5 with the following changes.

1. Cellulose: a return to the cycle of the pulp of corrugated containers, containing 2.8% of Soaps of tall oil and black liquor, as evidenced by the presence of charge is equal to 0.85 of mkaku/g, soluble polyanionic crushed to the consistency of grind 552 Canadian Standard Freeness (CSF) at pH 8.

2. Standard hard water: standard hard water with an alkalinity of 50 ppm million and hardness 100 ppm million prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 7.2 using NaOH.

3. The agent that reduces the foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 9.5 mol.% methacryloxypropyltrimethoxysilane and 90,5 mol.% acrylamide with the per 9,5 DL/g

6. Lignosulfonate: D-419-5, Lignotech USA. Lignosulfonate calcium.

The results are shown in table. 7. Smilest supplements. However, this result is compensated by the lower viscosity of the mixture, making the process more automated.

Examples 47-52.

These examples show the effectiveness of other polyvalent cations compared with alum. The leaves were made by car Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) according to the procedure of examples 1-5 with the following changes.

1. Pulp: unbleached Kraft pulp Western rocks crushed to the consistency of grind 620 Canadian Standard Freeness (CSF) at pH 8.

2. Standard hard water: standard hard water with an alkalinity of 50 ppm million and hardness 100 ppm million prepared by adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4.

3. Agent, a reducing foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Polyaluminium: PHACSIZE, Diachem.

6. The ferric chloride: FeCl3.

7. Sulphate of iron: Fe2(SO4)3.

8. The cationic polymer is a copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

9. Cationic polymer B: a copolymer of 9.5 is the first liquor (Jefferson Smurfit Corporation): total number of solid particles 40,5% (according to TAPPI Standard T656),

Lignin: 11,9% (UV spectroscopy).

The charge density (colloidal titration): 0,111 mEq/g at pH of 9.0.

11. Lignosulfonate: D-419-5, Lignotech USA. Lignosulfonate calcium.

The results are shown in table. 8. Adding polyaluminosilicate (example 50), iron chloride (example 51) or iron sulfate (example 52) leads to the same increase paper strength, and that the addition of alum (example 49), compared with paper made using only the anionic and cationic polymer (example 48).

Examples 53-60.

These examples show that increasing the strength according to this invention is achieved even in the case when alum, polymer, and black liquor added to raw materials for the manufacture of paper in a wide range of pH. The sheets are produced on the machine Noble and Wood Sheet Machine (Noble and Wood Machine Co., Hoosick Falls, NY) in accordance with the procedure of examples 1-5 with the following changes.

1. The pulp: unbleached Kraft pulp southern rocks containing 0.4% Soaps of tall oil and black liquor, as evidenced by the presence of a charge equal to 0.45 mkaku/g u-soluble polyanionic polymer, at a pH of 9.0, crushed to the point of grinding according 693 Canadian Standard Freeness (CSF) at pH 8.0.

2. With the Jena adding CaCl2and NaHCO3to the distilled water and bring the pH to 5.5 using H2SO4.

3. The agent that reduces the foaming: Defoamer 491A (Hercules Incorporated, Wilmington, DE).

4. Alum: aluminum sulfate Al2(SO4)318H2O.

5. Cationic polymer: copolymer of 6.2 mol.% diallyldimethylammoniumchloride and 93.8 mol.% acrylamide, with the per 12,2 DL/g

6. Black liquor (Jefferson Smurfit Corporation): total solids content of 40.5% (according to TAPPI Standard T650).

Lignin: 11,9% (UV spectroscopy).

The charge density (colloidal titration): 0,111 mEq/g at pH of 9.0.

The results are shown in table. 9. These examples show that alum, polymer, and black liquor can be added to the feedstock at a pH in the range of from about 6.0 to 11.0. The value of the strength is almost independent from the pH at which they are added.

Although this invention is described with respect to specific aspects, it should be borne in mind that they do not limit the invention, and, without going beyond its scope, can make various changes and modifications.

1. A method of obtaining a water suspension for making paper containing polyelectrolyte complex vkljuchajuwih compounds; b) adding to the aqueous suspension of water-soluble cationic polymer and a water-soluble anionic polymer, which is able to interact in aqueous suspension with the formation of polyelectrolyte complex, and compounds containing multivalent cation having a charge equal to at least +3; C) formation of a polyelectrolyte complex, in which the indicated compound containing a polyvalent cation, add in the concentration, which provides the number of cation equivalent on a molar basis, the amount of aluminum contained in the alum added at a concentration of from about 1.5% to about 6% (based on dry weight of cellulosic fibers.

2. The method according to p. 1 in which the aqueous suspension of cellulose fibres, containing surface-active carboxyl-containing compounds, also contains water-soluble anionic polymer that can interact with water-soluble cationic polymer with the formation of the polyelectrolyte complex.

3. A method of obtaining a water suspension for making paper containing polyelectrolyte complex comprising (a) preparation of an aqueous suspension comprising cellulosic fibres, surface-active carboxylcontaining polymer, which is able to interact with the anionic polymer and the aqueous suspension with the formation of polyelectrolyte complex, and compounds containing multivalent cation having a charge equal to at least +3; C) formation of a polyelectrolyte complex, in which the indicated compound containing a polyvalent cation, add in the concentration, which provides the number of cation equivalent on a molar basis, the amount of aluminum contained in the alum added at a concentration of from about 1.5% to about 6% (based on dry weight of cellulosic fibers.

4. The method according to any of the preceding paragraphs, in which the cationic polymer is a linear polymer.

5. The method according to any of the preceding paragraphs, in which the surface-active carboxyl-containing compounds are present in an amount of from about 0.05 to about 10% by weight of dry pulp fibers.

6. The method according to any of the preceding paragraphs, in which the polyvalent cation having a charge equal to at least +3, is the aluminum contained in alum.

7. The method according to p. 6, in which alum is added in an amount of from about 1.5% to about 2.5% based on the weight of dry cellulose fibers, and cationic polymer are mixed with each other before they are added to the aqueous suspension.

9. The method according to p. 1 or 2, which uses the following order of addition: 1) a compound containing a polyvalent cation, 2) a cationic polymer, and (3) anionic polymer.

10. The method according to any of the preceding paragraphs, in which the water-soluble cationic polymer is characterized by the results of the specific viscosity (0,05% by weight solution in 2 m aqueous solution of NaCl at 30oC) greater than 2 DL/g and a charge density from about 0.2 to about 4 mEq/g, and a water-soluble anionic polymer has a charge density of less than about 5 mEq/g

11. The method according to any of the preceding paragraphs, in which the amount of cationic polymer is from about 0.1% to about 5% based on the weight of dry pulp fibers.

12. The method according to any of the preceding paragraphs, in which the amount of cationic polymer is from about 0.2% to about 3%.

13. The method according to any of the preceding paragraphs, in which the amount of cationic polymer is from about 0.3% to about 1%.

14. The method according to any of the previous paragraphs, in which the amount of anionic polymer is 0.1 - 25% Resto anionic polymer is 0.2 - 5% based on the weight of dry pulp fibers.

16. The method according to any of the preceding paragraphs, in which the amount of anionic polymer is 0.25 - 2.5% based on the weight of dry pulp fibers.

17. The method according to any of the preceding paragraphs, in which the cationic polymer is selected from the group consisting of cationic guar and copolymers of acrylamide and diallyldimethylammoniumchloride, acryloyldimethyltaurate, methacryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane and metallicametallicametall.

18. The method according to p. 17, in which the cationic polymer is a copolymer of acrylamide with diallyldimethylammoniumchloride or methacryloxypropyltrimethoxysilane.

19. The method according to any of the preceding paragraphs, in which the anionic polymer is selected from the group consisting of anionic substances usually contained in the cellulose, synthetic anionic polymers and modified to give the anionic nature of natural polymers.

20. The method according to p. 19, in which the anionic substances usually contained in the cellulose selected from the group consisting of solubilizing lignins and hemicelluloses, with the dust, consisting of copolymers of acrylamide and sodium acrylate, sodium methacrylate and sodium 2-acrylamide-2-methyl propane sulfate, and poly(sodium 2-acrylamide-2-methyl propane sulfate); and modified to give the anionic nature of the natural polymers are selected from the group consisting of sodium salt of carboxymethyl cellulose, carboxymethylstarch sodium, sodium alginate and polypectomy sodium.

21. The method according to p. 1,2 or 3, wherein the cellulose is a unbleached cellulose, cationic polymer is a copolymer of acrylamide with diallyldimethylammoniumchloride or methacryloxypropyltrimethoxysilane, the anionic polymer is a lignosulfonate and a compound containing a polyvalent cation having a charge equal to at least +3, is an alum.

22. The method according to any of paragraphs.6 - 21, in which the quantity of alum is from about 1.5% to about 6% by weight, the amount of cationic polymer is from about 0.1 % to about 5% by weight and the amount of anionic polymer is from about 0.1% to about 25% by weight based on the weight of dry pulp fibers.

23. The method according to p. 21, in which the amount of a copolymer of acrylamide with dalidio 5% by weight, the amount of lignosulfonate is from about 0.1% to about 25% by weight and the amount of alum is from about 1.5% to about 6% based on the weight of dry pulp fibers.

24. Paper made from aqueous suspensions obtained by the method according to any of paragraphs. 1 - 23, followed by manufacture of the specified suspension of leaves and drying to obtain a paper with high strength.

 

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EFFECT: increased activity for drying due to a reduction in the amount of polymer.

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