EP0763159B1 - Method for making paper - Google Patents

Abstract

PCT No. PCT/FR96/00468 Sec. 371 Date Jan. 13, 1997 Sec. 102(e) Date Jan. 13, 1997 PCT Filed Mar. 28, 1996 PCT Pub. No. WO96/30591 PCT Pub. Date Oct. 3, 1996The invention relates to a new process for the manufacture of paper which employs, in the fibrous composition, a cationic starch exhibiting a high level of fixed nitrogen, namely greater than 0.95%, and a polyaluminum compound, such as a (basic) aluminum polychloride or an aluminum polychlorosulphate. This process makes it possible, including under difficult conditions (fibrous composition based on old papers, significant closure of the circuits), to improve the level of retention of starch and the physical characteristics of the paper, indeed to increase the machine speed by dispensing with the surface treatment optionally applied to the paper. The process according to the invention is particularly suitable for the manufacture of paper for graphical use or of paper for wrapping or packaging and very particularly of fluting paper or of liner paper for corrugated fiberboard.

Description

• de fibres synthétiques telles que les fibres de polyamides, de polyesters et de résines polyacryliques,
• de fibres minérales telles que les fibres d'amiante, de céramique et de verre,
• de toutes combinaisons de fibres cellulosiques, synthétiques et minérales.

The subject of the invention is a new method of manufacturing paper according to claim 1, a corrugated paper according to claim 11 and a use according to claim 12, the term "paper" designating in the following any planar structure or sheet not only based on cellulose fibers - the most frequently used raw material in the paper and cardboard industry - but also based on:

• synthetic fibers such as polyamide, polyester and polyacrylic resin fibers,
• mineral fibers such as asbestos, ceramic and glass fibers,
• all combinations of cellulosic, synthetic and mineral fibers.

The well-known use of cationic starches which are introduced into the fiber mass before the leaf formation, overall increased the retention of fibers and fillers, improve drainage and to increase the physical characteristics of the paper. In effect, the preferential fixing of these starches on the anionic reaction sites of fibers and fillers, made possible by their cationic character or cationicity, increases the number of bonds between fibers as well as between fibers and fillers, resulting in resistance larger paper. Thanks to this greater resistance paper, it became possible to decrease the concentration of the mass of fibers or to use fibers of inferior quality.

However, it turns out that in recent years, the aforementioned benefits provided by the implementation of cationic starches do not always compensate the growing disadvantages created by degradation increasing the quality of raw materials.

Indeed, to deal with concerns of increasingly stringent economic profitability, not only the semi-chemical paste traditionally used for example for the production of paper for corrugated board saw its share reduced in favor of pulp from fibers recovery cellulosics, commonly called FCR, but more and more the very quality of these FCRs is more and more poor due to the increasing number of recycling of "old paper".

Added to this is the fact that at the level of paper, the trend is more and more towards closure systematic circuits, resulting in enriched waters in suspended solids, organic and mineral. Among these undesirable or polluting materials, finds, in particular, very physicochemical species varied, including colloidal in nature, presenting a anionic character and commonly grouped under generic terms of "anionic trash" or "waste anionic ".

Their ever increasing presence in waters that any cationic starch used happens to be always more requested to neutralize or attach to said anionic waste and, correspondingly, always less available to settle on sites reactive fibers, hence an increase in the rate starch not retained on the sheet and less resistance of it.

In general, whatever the degree of cationicity of starches, closing of circuits and deterioration in fiber quality results in a inevitable decrease in efficiency (including retention on the leaf) of the starches and the solidity of papers as well as by a quasi-systematic increase sewage treatment water treatment needs paper also called "water under canvas".

Assuming that the effectiveness of a starch cationic must be greater as its probability of fixation on the fibers was high, we used to increase the likelihood of fixation to associations such as "cationic starch - polyacrylamide "(US patent 4,066,495)," cationic starch - alumina sulfate "or" cationic starch - basic salt aluminum "(patent FR 2,418,297).

We also used, as described in European patent EP 0 139 597 issued in the name of the Company Applicant, to associations "cereal starch cationic - cationic tuber starch ", said starches advantageously exhibiting, according to the examples of said patent, a relatively low rate of nitrogen fixed on dry high, namely between 0.20 and 0.30%.

The aforementioned technology combining starch cationic and basic aluminum salt was the subject, especially since the end of the 80s, numerous studies in order to remain constantly adapted to order requirements technical (general paper quality), economical (speed machines, in particular) and regulatory (defense of environment in particular) which stationers.

These requirements had in particular the effect of advocate, as described in the European patent EP 0 276 200, to combine a cationic polysaccharide and a anionic aluminum compound, which is generally formed in situ by using alkali, and this, under conditions such as the pH of the mass fibrous should be kept at a specific value (7 to 8) at a specific location on the paper machine, i.e. immediately before the headbox.

1) pour des ratios molaires très précis entre anions (apportés par l'alcali - exemples : OH^- ou CO₃ ^2-) et cations (Al³⁺, apportés par le composé aluminium),

2) et pour un ordre précis d'introduction des additifs dans la masse fibreuse, à savoir le composé aluminium puis le polysaccharide cationique.

Reading this patent EP 0 276 200 shows, however, that such anionic aluminum compound / cationic polysaccharide associations only make it possible to obtain the desired effect, namely obtaining good charge or fine retention, only under conditions specific operating procedures and in particular:

1) for very precise molar ratios between anions (provided by alkali - examples: OH ^- or CO ₃ ^2- ) and cations (Al ³⁺ , provided by the aluminum compound),

2) and for a precise order of introduction of the additives into the fibrous mass, namely the aluminum compound then the cationic polysaccharide.

It should also be noted that patent EP 0 276 200 does not in no way discloses the retention rate that can be obtained as regards the cationic starch used ("CATO 102" product with a fixed nitrogen level of About 0.30%), nor the physical characteristics of the paper resulting from the implementation of such associations cationic polymer / anionic aluminum compound ".

• soit, comme décrit dans le brevet européen EP 285.486, d'augmenter le niveau d'introduction de l'amidon cationique jusqu'à des taux de l'ordre de 5 % exprimé en poids par rapport au poids de fibres et ce, en association avec un polychlorure d'aluminium lequel est, de préférence, mis en oeuvre le plus près possible de la caisse de tête de la machine à papier,
• soit, comme décrit dans le brevet européen EP 285.487, de maintenir des taux relativement faibles d'amidon cationique (0,3 - 0,4 % en poids de fibres) mais en associant obligatoirement ledit amidon, outre à un polychlorure d'aluminium, à une charge minérale (notamment du carbonate de calcium) et à un agent de collage (notamment de type alkyl cétène dimère ou "AKD" ou de type anhydride d'acide succinique ou "ASA").

The technical, economic and regulatory requirements mentioned above have had the effect of also recommending:

• or, as described in European patent EP 285,486, of increasing the level of introduction of cationic starch up to rates of the order of 5% expressed by weight relative to the weight of fibers and this, in combination with a poly aluminum chloride which is preferably used as close as possible to the headbox of the paper machine,
• either, as described in European patent EP 285,487, to maintain relatively low levels of cationic starch (0.3 - 0.4% by weight of fibers) but by necessarily associating said starch, in addition to a polychloride of aluminum, a mineral filler (in particular calcium carbonate) and a sizing agent (in particular of the alkyl ketene dimer type or "AKD" or of the succinic acid anhydride type or "ASA").

It should be noted that these two adjustments made to the "cationic starch - basic aluminum salt" technology mainly expressed for "headbox" pH with a value of 7.2 or higher (up to 7.8), respectively, for the production of type paper "corrugated cardboard cover", surfaced with starch native (patent EP 285,486) or of the "printing and writing "," Offset printing "or" reprography "(patent EP 285.487).

Furthermore, these two documents do not disclose in no way does the retention rate of the cationic starch put in use and, by difference, the level of cationic starch who may not have settled within the leaf in formation and thereby contribute to organic pollution and the non profitability of the system.

Furthermore, no details are given as to the nature of the cationic starch used in the context of these two documents (fixed nitrogen level, viscosity, origin botany, etc ...).

Very recently, it has been envisaged to associate different starches of variable cationicity (DS from 0.032 to 0.11 corresponding to nitrogen levels of 0.28 to 0.95) to various synthetic products capable of reducing the effects undesirable inherent in the presence, in the circuits, of anionic waste (GLITTENBERG et al. in "PAPER TECHNOLOGY ", Vol 35 N ° 7, pp 18-27).

It appears that among these waste collectors anionic ("anionic trash catchers") type products PEI (polyethylene imine) or p-DADMAC (poly di chloride alkyl dimethyl ammonium) are more effective than poly aluminum chloride (the chemical composition of which is not not specified), which is presented as "practically ineffective in terms of retention. "

• ne décrit aucunement les caractéristiques physiques du papier que l'on peut obtenir en associant un amidon cationique et un polychlorure d'aluminium,
• montre que pour certains paramètres un amidon cationique de DS 0,11 n'est pas significativement plus efficace qu'un amidon cationique de DS de 0,032 ou 0,035,
• n'étudie réellement les caractéristiques physiques du papier, évaluées sur "Formette de Rétention", que dans le cadre d'associations amidon cationique / P-DADMAC et ce avec mise en oeuvre d'un amidon (produit C* BOND 05906) lequel est connu pour présenter un taux d'azote relativement peu élevé, en tous cas inférieur à 0,5 %,
• détourne globalement l'homme de l'art d'envisager des amidons cationiques de plus hauts DS, et donc de taux d'azote plus élevés, lesquels seraient "non intéressants d'un point de vue économique".

In any event, we note that this document:

• does not in any way describe the physical characteristics of the paper which can be obtained by combining a cationic starch and a poly aluminum chloride
• shows that for certain parameters a cationic starch with DS 0.11 is not significantly more effective than a cationic starch with DS of 0.032 or 0.035,
• really studies the physical characteristics of the paper, evaluated on "Retention Form", only in the context of cationic starch / P-DADMAC associations and this with the use of a starch (product C * BOND 05906) which is known to have a relatively low nitrogen level, in any case less than 0.5%,
• globally diverts those skilled in the art to consider cationic starches with higher DS, and therefore higher nitrogen levels, which would be "not interesting from an economic point of view".

To improve the efficiency of starches the strength of the papers and / or lower the rate of undesirable suspended solids contained in waters under canvas and secondary effluents ("waters clarified "), it was also proposed to use polysaccharide binders, and in particular starches, containing both cationic groups and anionic groups as described in the patents FR 2,289,674, EP 257,338 and the patent application WO 81/00147.

Patent FR 2,289,674 describes the implementation specific, in environments highly concentrated in sulfate alumina, amphoteric starches of the sulfo-succinate type reduced cationicity (degree of substitution or "DS" announced 0.03 corresponding to a fixed nitrogen level lower than 0.30% based on the dry weight of the starch) and this, in view improve the retention of pigments of the dioxide type titanium. In some cases, the physical characteristics of the paper, expressed by the MULLEN index alone, can be improved but very limited (MULLEN max obtained: 1.59).

Patent EP 257,338 describes the implementation specific for amphoteric phosphate-type starches, in particular waxy base, cationicity qualifying as "low" or "average" (maximum DS of 0.08 corresponding to a nitrogen content fixed less than 0.7% / dry weight of starch). This document considers the interest of such amphoteric starches only in the only prospect of improving drainage performance of the paper machine.

Patent application WO 81/00147 describes the preparation, in a complicated process, of mucus amphoteric based on cationic starch of reduced cationicity and a CMC type polymer, intended to coat a load / fiber structure.

In any event, the complexity and cost of preparation, insufficient performance and / or limited potential for application of such starches amphoteric reduce the industrial interest.

To improve the efficiency of starches the strength of the papers and / or lower the pollution levels of effluents from the activity paper mill, so-called techniques have also been recommended "dual" by which one associates on the one hand polymers cationic and secondly anionic compounds of mineral and / or organic origin. Such a technique, using separately a cationic starch and a anionic starch, is particularly recommended at the level of EP 282,415 of which the Applicant Company is holder.

Another dual technique is also described in patent EP 41.056, claiming the association between starch cationic and colloidal silicic acid. Such a association has been improved over time as it follows from the description of the request for WO 86/00100 (anionic agent of silicate type) aluminum or silicic acid modified by aluminum), Patent EP 348,366 (anionic agent of silicic acid type polymer with a specific surface area) and of patent EP 490,425 (cationic agent containing from 0.05 to 0.5% by weight of aluminum).

In general, it appears that the technique dual using a silicic derivative as an agent anionic had to be considerably complexified during time to meet the requirements (technical, increasingly pressing) faced by papermakers.

• des systèmes ternaires "amidon cationique (DS = 0,035) / polymère d'acide silicique particulier / sel d'aluminium" comme décrit au niveau du brevet EP 349.366 précité, ledit sel d'aluminium étant préférentiellement choisi parmi l'alun, l'aluminate de sodium ou le chlorure d'aluminium, et
• en dernier lieu, des systèmes binaires mettant en oeuvre des amidons cationiques porteurs d'aluminium préparés selon des procédés complexes comme il résulte de la lecture des brevets EP 303.039 ou EP 303.040, cités au niveau du brevet EP 490.425 susmentionné.

We were thus led to design:

• ternary systems "cationic starch (DS = 0.035) / specific silicic acid polymer / aluminum salt" as described in the abovementioned patent EP 349,366, said aluminum salt being preferably chosen from alum, aluminate sodium or aluminum chloride, and
• lastly, binary systems using cationic aluminum-bearing starches prepared according to complex methods as it results from reading the patents EP 303,039 or EP 303,040, cited in the patent EP 490,425 mentioned above.

In addition, patents EP 349,366 and 490,425 are mainly focused on the "draining" and / or "retention" and do not actually address the study of physical characteristics of the paper.

These dual techniques based on silicic derivative lead, as pointed out, to an improvement in the retention, thus making it possible to manufacture higher filler content. They save money substantial cellulose, but not applicable in all cases. In addition, the amount of starch attached to the cellulose at the time of the formation of the remaining sheet still limited, the physical characteristics of the paper obtained are not always improved sufficiently.

To improve physical characteristics loaded and pasted paper, it was recently recommended (EP 522,940 patent) much more sophisticated systems made up of a so-called "retention system" based on three constituents, in this case a cationic starch (DS of 0.01 to 0.1 corresponding to fixed nitrogen levels <0.9%), of an aluminum and anionic silica chloride, constituents whose introduction rates must also be included in very specific ranges.

We note that if such a retentive system ternary, based on the silica / polychloride synergy aluminum, specifically improves the appearance of paper (i, e the homogeneity of the fibers in the plane and the thickness of the sheet), said system does not allow achieve retention rates (total retention) of at least 80%.

It follows from all of the above that it there is a real need to provide a means to make paper that is simple, profitable, not generator of pollution problems and able to meet the current requirements of paper manufacturers in particular in terms of the nature of the raw material (FCR for corrugated paper for example), quality finished product (sheet resistance in particular), productivity (machine speed).

In particular, there is a real need to find a means of making paper in conditions which meet the practice's requirements and which does not impose the systematic use of starches amphoteric, starches of different ionicities and / or complex silica-based systems.

And the merit of the Applicant Company has been find that such a means could be established, including under conditions deemed difficult (dough consisting of FCR or old paper, significant closure of circuits), by using on the one hand a cationic starch with a sufficiently high nitrogen level and other part of a particular aluminum compound.

More precisely, the present invention has for object a process for making paper from a fibrous composition characterized by the fact that one puts said fibrous composition, in contact, simultaneously or no, with at least one cationic starch having a level fixed nitrogen greater than 0.95%, expressed on the dry weight starch and with at least one polyaluminium compound.

The cationic starches used in accordance to the invention can be obtained by any technique current or future, in aqueous medium, in solvent medium or in the dry phase, suitable for allowing one or more nitrogen group (s) of electropositive nature to settle on a starch or a mixture of starches of all kinds and origins when the nitrogen rate thus fixed is greater than 0.95% by weight of dry starch.

• brevet FR 2.434.821, en particulier de la page 3, ligne 29 à la page 5, ligne 10,
• brevet EP 139.597, en particulier colonne 1, lignes 30 à 52, et
• brevet EP 282.415, en particulier page 4, lignes 5 à 36.

Said nitrogen groups may in particular contain a tertiary or quaternary nitrogen atom such as the reagents described in the following patents, filed in the name of the Applicant:

• Patent FR 2,434,821, in particular from page 3, line 29 to page 5, line 10,
• EP 139,597, in particular column 1, lines 30 to 52, and
• Patent EP 282,415, in particular page 4, lines 5 to 36.

Cationic starches used in the process according to the invention can in particular be prepared by one any of the cationization techniques, in particular cationization in the dry phase, described in the patents FR 2,434,821, FR 2,477,159, EP 233,336, EP 303,039, EP 333,292, EP 406,837, US 4,332,935 and US 429,444.

The cationic starches used according to the invention may moreover be of a nature "polycationic" such as those described in the patents EP 406,837 and US 429,444 cited above since said starches ultimately have a higher fixed nitrogen level at 0.95% on the dry weight of starch.

Preferably, in the context of the invention, use of starches with a fixed nitrogen level from about 1.0% to about 3.0%, preferably from about 1.0% to around 2.5%, and even more preferably from 1% to 1.6%, based on the dry weight of starch.

Said starches, of natural or hybrid origin, may be potato based, potato to high amylopectin (waxy starch), corn, wheat, corn high amylopectin (waxy corn), high corn amylose, rice, pea or cassava content, based on cuts or fractions that can be made or obtained from it such as amylose, amylopectin, particle size sections known to those skilled in the art under the terms of starch from wheat "A" and wheat starch "B", and any mixtures at least any two of the above products.

As such, the cationic starch usable for the manufacture of the paper according to the invention can in particular be consisting of a mixture of at least one tuber starch cationic, especially potato starch cationic and at least one cationic cereal starch, in particular of cationic corn or wheat.

It is in particular possible to use mixtures with potato starch weight ratios cationic / wheat or cationic corn ranging from about 10/90 at around 90/10, and in particular from 20/80 to 80/20, being understood that the cationization may have been carried out, as described at the level of patent EP 139,597 in the name of Applicant, on the mixture of the two starches or, so separate, on each of the two starches, which are then mixed.

The cationic starches used in the process manufacture of paper according to the invention, which have a fixed nitrogen level greater than 0.95% on the dry weight starch, can simultaneously, previously or after cationization, have been subjected to a any chemical and / or physical treatment.

The chemical treatment can notably consist of either of the known crosslinking techniques, oxidation, alkaline treatment, acid hydrolysis and / or enzymatic, esterification or plasticization.

By crosslinking technique is meant in particular any process involving an agent such as acid adipic or one of its derivatives, a halohydrin (by example epichlorohydrin), a trimetaphosphate (for example sodium), phosphorus oxychloride or a resin (for example based on formalin).

The term “oxidation technique” means in particular all non-degradative oxidation process allowing substitution at least one OH group of starch by a group COOH.

Among such methods, advantageously use of "selective" oxidation techniques, that is to say allowing substantial oxidation of the single terminal hemiacetal function of the starting starch, which can already be cationized before being thus oxidized selectively. Such techniques are described, among others, in terms of European patents EP 23 202 and EP 562,927.

By esterification techniques is meant in particular any process for replacing starch (already cationized or not), at least in one place, by acetate, phosphate, succinate, sulfo-succinate groups, alkenyl succinate, sulfate, maleate, propionate or carboxyl.

As a result, the starches used in the papermaking process according to the invention can consist of amphoteric starches, i.e. products which are both cationic (higher fixed nitrogen level at 0.95% / dry weight of starch) and anionic.

In terms of physical modification, starches cationic can easily be used (in order to be contacted with the fibrous composition) in the form of diluted aqueous adhesives of varying concentrations, generally less than 20%, preferably included between about 15% and about 1%.

The preparation of adhesives is carried out in a way known per se, by discontinuous or continuous cooking, by example, at 110-130 ° C, in a continuous pressure cooker or "jet-cooker" capable of ensuring the dosing operations, cooking and dilution.

According to an advantageous embodiment of the invention, it may be proposed to present the starch under the form of an uncooked or pregelatinized starch powder, this prior to and / or when brought into contact with the fibrous composition.

The Applicant Company has observed in particular that the high level of fixed nitrogen characteristic of the starches used in the context of the invention could allow these the latter to dissolve satisfactorily (i.e. not instantaneous but progressive) under conditions very significantly lower than those adopted in jet cooker, for example at temperatures between 10 and 50 ° C approximately. So powders starch can advantageously be brought into contact, by any suitable means, of fibrous compositions, the temperature is raised and / or maintained by any means suitable for a value of about 25 ° C to about 50 ° C.

Thus, the present invention allows, between others and by the nature of the starches it puts in work, to simplify certain manufacturing processes of paper by removing traditional means of cooking continuous or discontinuous starch.

According to another variant of the method according to the invention and regardless of how it is going to be then cooked and used in stationery, starch cationic has a viscosity of about 300 to about 3000, preferably from 350 to 2500, BRABENDER units (UB).

Said viscosity is measured on a "BRABENDER 350 CMG" type. A starch sample (25.0 g) is used in sufficient water to obtain a total load of 480 g. This is introduced in the viscometer cooking chamber. Cooking is done from controlled manner (1.5 ° C / min) and the viscosity of the glue after it has been worn and then maintained 20 minutes at a temperature of 92 ° C.

For information purposes only, the Applicant Company observed that cationic starches exhibiting a rate nitrogen fixed from 1 to 1.6% and a viscosity from 900 to 2100 UB were of particular interest in connection with the present invention.

According to another variant of the method according to the invention the cationic starch and the fibrous composition are brought into contact under conditions such as said cationic starch represents from about 0.2 to about 6%, from preferably 0.3 to 4%, and even more preferably from 0.7 to 3%, by weight of said fibrous composition.

Furthermore and as already specified, in the context of the present invention the particular cationic starch such that described above is associated with at least one "sensor anionic waste "of a particular type, namely a compound polyaluminium.

1. les sels de formule : Al_n(OH)_mX_{3n- m} dans laquelle X est Cl, NO₃ ou CH₃COO, n est quelconque, 3n-m est positif, m et n sont des nombres entiers positifs ; ledit sel pouvant contenir en outre un anion polyvalent Y choisi parmi les anions des acides sulfurique, phosphorique, polyphosphorique, silicique, chromique, carboxylique et sulfonique, le rapport molaire Y/Al étant de préférence compris entre 0,015 et 0,4 et la basicité ou le rapport m/3 n étant compris entre 0,1 et 0,9, de préférence entre 0,2 et 0,85. De tels sels peuvent notamment être constitués ou se rapprocher des produits "TENFLOC 18" ou "PAC 18" et "EKOFLOCK" fournis par EKA-NOBEL ou AKZO-NOBEL ;

2. les sels de formule : Al_n(OH)_mCl_{3n- m- 2k}(SO₄)_k dans laquelle k, m et n sont des entiers positifs, et 3n > m + 2k, la basicité ou le rapport m/3n est, de préférence, compris entre 0,3 et 0,7 et k/n de préférence compris entre 0,01 et 0,03.

3. les sels de formule : ( Al_n(OH)_{3n- m-2p} Cl_m(SO₄)_p )Z dans laquelle (3n- m- 2p)/3n = 0,4 à 0,7 ; p = 0,04 à 0,25 n ; m/p = 8 à 35 ; k, m, n, et p sont des nombres entiers et z est au moins 1 ;

4. les chlorosulfates d'aluminium basiques de formule : Al_nOH_m(SO₄)_kCl_{3n- m- 2k} dans laquelle la basicité ou le rapport molaire (m/3n)x100 est généralement compris entre 40 % environ et 65 % environ, qui présentent un rapport équivalent Al/équivalent Cl de préférence compris entre 2,8 et 5. Un sel correspondant à la formule IV consiste notamment en le WAC fourni par ELF-ATOCHEM ;

5. les sels de formule : ( Al(OH)x(SO₄)y(H2O)₃ )n ou x = 1,5 à 2,0 ; y = 0,5 à 0,75, x + 2y = 3 et z = 1,5 à 4,0.

By “polyaluminium compound” within the meaning of the present invention, is meant in particular the products which are commonly called “aluminum polyhydroxide” “aluminum polychloride”, “basic aluminum polychloride”, “basic aluminum polychloride "or" aluminum polysulfate "and preferably consists of one or more of the following products:

1. the salts of formula: Al _n (OH) _m X _{3n- m} where X is Cl, NO ₃ or CH ₃ COO, n is any, 3n-m is positive, m and n are positive integers; said salt possibly also containing a polyvalent anion Y chosen from anions of sulfuric, phosphoric, polyphosphoric, silicic, chromic, carboxylic and sulfonic acids, the molar ratio Y / Al preferably being between 0.015 and 0.4 and the basicity or the ratio m / 3 n being between 0.1 and 0.9, preferably between 0.2 and 0.85. Such salts can in particular consist of or come close to the products "TENFLOC 18" or "PAC 18" and "EKOFLOCK" supplied by EKA-NOBEL or AKZO-NOBEL;

2. the salts of formula: Al _n (OH) _m Cl _{3n- m- 2k} (SO ₄ ) _k in which k, m and n are positive integers, and 3n> m + 2k, the basicity or the ratio m / 3n is preferably between 0.3 and 0.7 and k / n preferably between 0 , 01 and 0.03.

3. the salts of formula: (Al _n (OH) _{3n- m-2p} Cl _m (SO ₄ ) _p ) Z in which (3n- m- 2p) / 3n = 0.4 to 0.7; p = 0.04 to 0.25 n; m / p = 8 to 35; k, m, n, and p are whole numbers and z is at least 1;

4. basic aluminum chlorosulfates of formula: Al _n OH _m (SO ₄ ) _k Cl _{3n- m- 2k} in which the basicity or the molar ratio (m / 3n) x100 is generally between approximately 40% and approximately 65%, which have an Al equivalent / Cl equivalent ratio preferably between 2.8 and 5. A salt corresponding to the formula IV consists in particular of the WAC supplied by ELF-ATOCHEM;

5. the salts of formula: (Al (OH) x (SO ₄ ) y (H2O) ₃ ) n or x = 1.5 to 2.0; y = 0.5 to 0.75, x + 2y = 3 and z = 1.5 to 4.0.

According to a variant of the invention the compound polyaluminium advantageously consists of a salt of formula I, II, IV or V and consists in particular of a product WAC, PAC 18 or EKOFLOCK type.

• demande de brevet FR 2.418.297, page 2, lignes 1 à 14,
• demande de brevet EP 522.940, page 3, lignes 19 à 49, et
• demande de brevet WO 94/01619, page 4, ligne 6 à page 5, ligne 17.

Such polyaluminium compounds are described in particular in the aforementioned documents:

• patent application FR 2.418.297, page 2, lines 1 to 14,
• Patent application EP 522,940, page 3, lines 19 to 49, and
• Patent application WO 94/01619, page 4, line 6 to page 5, line 17.

Preferably, the polyaluminium compounds used according to the present invention have an aluminum content, expressed as Al ₂ O ₃ , of approximately 8% to approximately 20% by weight, in particular from 10% to 18% by weight.

According to another variant of the process according to the invention, the polyaluminium compound and the fibrous composition are brought into contact under conditions such that said polyaluminium compound, expressed by weight of Al ₂ O ₃ , represents from approximately 0.01% to approximately 0.5%, preferably 0.015% to 0.4%, of the weight of said fibrous composition.

Regarding the conditions of contact between them, cationic starch, polyaluminium compound and the fibrous composition, it should be emphasized the very great and surprising flexibility of the manufacture of paper according to the invention.

Indeed and contrary to the general teachings the prior art, the process according to the invention does not require that the cationic starch be contact with the fibrous composition prior to polyaluminium compound, or vice versa than the compound polyaluminium is brought into contact with the composition fibrous before cationic starch. The society The Applicant even observed that it was entirely possible put the cationic starch and the polyaluminium compound simultaneously or almost simultaneously in contact with the fibrous composition.

In addition, it has been found that the compound polyaluminium could, in particular in circuits very closed, be introduced, in whole or in part, at the same level waters under canvas.

• mettre en contact l'amidon cationique avec la composition fibreuse entre un niveau correspondant au raffineur et un niveau se situant juste avant la caisse de tête, de préférence entre un niveau se situant juste après le raffineur et un niveau se situant juste avant la pompe de mélange de la machine à papier,
• mettre en contact le composé polyaluminium avec la composition fibreuse entre un niveau correspondant au raffineur et un niveau correspondant à la caisse de tête et/ou aux eaux sous toile et, de préférence, entre un niveau se situant juste après le raffineur et un niveau se situant juste avant la caisse de tête de la machine à papier.

Although it is possible, as explained above, to use the cationic starch and the polyaluminum compound in any order and at any location on the wet end of the paper machine, including the pulper the headbox, we prefer:

• bringing the cationic starch into contact with the fibrous composition between a level corresponding to the refiner and a level located just before the headbox, preferably between a level located just after the refiner and a level located just before the pump paper machine mixing,
• bringing the polyaluminium compound into contact with the fibrous composition between a level corresponding to the refiner and a level corresponding to the headbox and / or the waters under canvas and, preferably, between a level situated just after the refiner and a level located just before the headbox of the paper machine.

The polyaluminum compound can in particular be used contact of the fibrous composition between a level corresponding to the first vat room in the wet part of the paper machine and a level just after the purifier of the paper machine.

As noted, cationic starch and polyaluminium compound can be introduced in order indifferent to the level of the wet part of the machine paper, including being contacted simultaneously or almost simultaneously with the fibrous composition.

As a result, the period between the implementation contact of, respectively, either cationic starch or the polyaluminum compound with the fibrous composition and the contacting, respectively, either the compound polyaluminium or either cationic starch with the fibrous composition, is generally at most equal to 120 minutes approximately and in particular between 0 and 60 minutes, preferably between 0 and 45 minutes, and more preferably between 10 seconds and 40 minutes.

In practice, we will generally consider delays in the range of 25 seconds to 35 minutes, in particular 30 seconds to 20 minutes between the respective implementation of the two products (cationic starch and compound polyaluminium, in any order).

As previously stated and as it will result from the examples below, the manufacturing process of paper according to the present invention, inter alia as advantages, in addition to being simple and profitable, to allow, especially in difficult conditions (pasta made up FCR or old paper, significant closure of circuits), obtain good starch retention, improve physical characteristics of the paper and ensure a machine speed meeting practical requirements, or even improve said machine speed and therefore, overall, to improve the profitability of the system.

And surprisingly and unexpectedly, the Company Applicant has found that the implementation, simultaneous or no, a polyaluminum compound and a cationic starch with a high fixed nitrogen level, in accordance with the invention made it possible, in particular, to remove all or part of certain surface treatments applied to the sheet after its formation.

Indeed, to obtain a paper (in particular a paper obtained under difficult conditions) having acceptable or increased mechanical characteristics, it is generally necessary to subject the paper produced to a surface treatment carried out in particular using a "size-press" type machine. Such treatment, applied on any one or on both sides of the paper, allows generally increase the proportion of starch, native or physically and / or chemically modified, entering the constitution of this paper, thus giving it a better resistance.

However, such a solution is not satisfactory from the economically, any additional operation being expensive. The transition to "size-press" leads, in addition additional cost related to equipment and operation additional drying it induces, a decrease significant, generally around 15 to 25%, of the speed of machines and therefore of paper production.

As a result, the method according to the invention is characterized by the fact that the paper obtained is not submitted, on any one of its two faces or even on the whole on both sides, no surface treatment highlighting uses a starch, native or physically modified and / or chemically.

Another major advantage of the manufacture of paper according to the invention is, as indicated previously, to allow, with respect to the techniques of the prior art, to obtain a starch retention rate without negatively influencing physical characteristics of the paper and / or obtain improved physical characteristics of the paper without negatively influence the starch retention rate.

Furthermore and quite remarkably, the process object of the present invention is susceptible, including included in difficult conditions (pasta based on FCR or old paper, significant closure of circuits) significantly improve both the retention rate starch and the physical characteristics of the paper, like it will be exemplified below.

In the context of the present invention, the concept of paper is not, as specified at the beginning of the description, in no way limiting and includes, in particular, papers for graphic uses (in particular for printing-writing, for inkjet printing, for printing Offset, for reprography) and papers for packaging and packaging (papers for corrugated, for packaging flexible type thin kraft or others).

The Applicant Company has observed in particular that the process according to the invention was particularly well suited for the production of cover or groove type paper for corrugated cardboard.

In particular, the method according to the invention allows obtaining corrugated paper for corrugated in improved conditions (starch retention, machine speed) compared to the techniques of the prior art and / or having improved characteristics compared to say technical.

• être appliqué à la fabrication de papier cannelure pour ondulé, non surfacé, présentant des caractéristiques physiques, tout à fait compatibles avec les exigences actuelles de la pratique, lesdites caractéristiques étant exprimées, comme indiqué ci-après, en "indice CMT" (selon norme NF Q03-044 ou ISO 7263) et en "indice MULLEN" (indice d'éclatement selon norme NF Q03-053 ou ISO 2758).

The Applicant Company in particular has highlighted that the process according to the invention is particularly suitable for:

• be applied to the manufacture of corrugated paper for corrugated, non-surfaced, having physical characteristics, entirely compatible with the current requirements of the practice, said characteristics being expressed, as indicated below, in "CMT index" (according to standard NF Q03-044 or ISO 7263) and in "MULLEN index" (burst index according to standard NF Q03-053 or ISO 2758).

As a result, the present invention is characterized in that the paper obtained is a graphic use or paper for packaging or packaging, in particular a corrugated paper or a cover paper for corrugated cardboard.

• un indice CMT 60 d'au moins 130 environ, de préférence d'au moins 135 environ, exprimé en N,
• un indice MULLEN d'au moins 1,65 environ, de préférence d'au moins 1,70 environ, exprimé en KPa/g.m^{2 -1}.

In particular, the process according to the invention makes it possible to prepare a corrugated paper for non-surfaced corrugated cardboard, with a grammage of 120 to 130 g / m ² , in particular obtained from old paper, having:

• a CMT 60 index of at least about 130, preferably at least about 135, expressed in N,
• a MULLEN index of at least about 1.65, preferably at least about 1.70, expressed in KPa / gm ^{2 -1} .

To the knowledge of the Applicant, such papers constitute new industrial products.

In addition, the fibrous composition which is made call in the context of the present invention presents, advantageously a pH called "neutral" or "pseudo neutral", at know from about 6.0 to about 8.0, preferably from 6.1 to 7.1, said pH being controllable or uncontrolled ("pH free ") as can be the case under conditions difficult to operate.

As a result of which the present invention is also characterized in that the fibrous composition has a pH, controlled or uncontrolled, between approximately 6.0 and approximately 8.0 and preferably between 6.1 and 7.1.

In addition, said fibrous composition may contain and / or be put in contact, if necessary, with one or the other of the products recommended in the aforementioned patents in level of prior art, including at least one product chosen from anionic starches, such as starches phosphorylated or sulfosuccinylated, bonding agents such than dimer aklyl ketene and acid anhydrides succinic, fillers, such as calcium carbonate and kaolin, retention agents such as polyacrylamides, polyethylene imines, poly chlorides alkyl ammonium and other synthetic retention agents, silicic and aluminosilicate compounds.

In particular, said fibrous composition can, advantageously and at any time, contain and / or be used in contact with a silica or aluminosilicon compound such than those described in patents EP 41 056 and EP 0 522 940 mentioned above and, optionally, a bonding agent and / or a charge.

This silica or aluminosilicon compound can be introduced into the fibrous composition simultaneously starch or at a different time, later or anterior, usually spaced a few seconds a few minutes from the time of the introduction of said starch cationic.

As a result of which, the process for manufacturing paper according to the invention is also characterized in that the fibrous composition is brought into contact at any time before the formation of the sheet, with at least one silica or aluminosilicon compound, in particular with a colloidal silicic acid, the particles of which have a specific surface of approximately 50 to approximately 1000 m ² / g, as well as possibly with at least one filler or a bonding agent.

The invention can be understood even better. using the examples which follow and which show some particularly advantageous modes of the manufacturing process of paper according to the invention.

EXAMPLE 1

From a thick pulp made from old paper, a fibrous composition (pulp) is reconstituted, by dilution in water, having the following main characteristics: pH 6.6 Total concentration 16.8 g / l Soluble concentration 13.7 g / l Acidity 0.24 g / l Resistivity 150 ohms Total ash 12.4 g / l Soluble ash 8.9 g / l

In the context of this example, representative of difficult paper preparation conditions, we study the performance (starch retention rate, MULLEN index and CMT 60 index) of the various cationic or amphoteric starches below in association or not with a polyaluminium compound hereafter designated by the generic term of "CPA". STARCH A Cationic (potato) starch with a fixed nitrogen level of about 1% on the dry weight of starch. STARCH B 25/75 mixture of a cationic starch and a cationic wheat starch, with a fixed nitrogen level of approximately 1.2%. STARCH C Cationic starch at 0.8% fixed nitrogen. STARCH D 25/75 mixture of cationic starch / cationic wheat at 0.65% fixed nitrogen. STARCH E Waxy amphoteric phosphate-type corn starch with a fixed nitrogen level of 0.25%. STARCH F Amphoteric starch of the sulfosuccinate type with a fixed nitrogen level of 0.25%.

• lait à 10 % de matière sèche (MS),
• température de cuisson : 120°C,
• durée de cuisson : 20 secondes,
• dilution en ligne : 700 l/heure
• absence de pompe en sortie cuiseur.

All of these starches were prepared in the form of adhesives on a continuous cooking appliance under the following conditions:

• milk with 10% dry matter (DM),
• cooking temperature: 120 ° C,
• cooking time: 20 seconds,
• online dilution: 700 l / hour
• no pump at the cooker outlet.

These different cationic or amphoteric starches are tested in combination or not with a PCA, in the occurrence of the "PAC 18" and this, on a "formette of TECHPAP automated retention.

The implementation, for these tests, is carried out at 2% starch and, when present, 1% CPA.

The contact time between the starch and the composition fibrous is 5 minutes. The contact time between the CPA (when used) and the fibrous composition is of 6 minutes.

• taux d'amidon fixé, ci-après désigné "RA", en %,
• indice MULLEN, ci-après désigné "MULLEN", en KPa/g/m² (selon la norme NF Q03-053 ou ISO 2758),
• indice CMT 60, ci-après désigné "CMT", en N (selon la norme NF Q03-044 ou ISO 7263).

For each of the starches A to G, in combination or not with a CPA ("PAC 18"), the following parameters are measured:

• fixed starch rate, hereinafter referred to as "RA", in%,
• MULLEN index, hereinafter referred to as "MULLEN", in KPa / g / m ² (according to standard NF Q03-053 or ISO 2758),
• CMT 60 index, hereinafter referred to as "CMT", in N (according to standard NF Q03-044 or ISO 7263).

It should be remembered that the MULLEN index allows to assess the burst strength of a paper (by example corrugated cover paper) subject to increasing hydrostatic pressure perpendicular to its surface, said index taking into account the grammage of said paper.

The CMT 60 index is particularly suited to the evaluation of corrugated cardboard paper and including the determination of resistance to flat compression of such paper.

As a reference test, we study the performances obtained in the absence of any starch and any CPA (TEST 1) or in the absence of starch but in the presence of CPA (TEST 2).

The results obtained ("RA", "MULLEN" and "CMT" as defined above) are detailed below according to the type of starch and the presence or absence of CPA. TRIAL TYPE OF STARCH CPA RA MULLEN CMT 1 - - - 1.42 117 2 - + - 1.32 120 3 AT - 44 1.51 134 4 AT + 60 1.74 136 5 B - 46 1.53 133 6 B + 62 1.75 142 7 VS - 48 1.64 132 8 VS + 56 1.72 125 9 D - 25 1.63 140 10 D + 19 1.54 148 11 E - ND 1.61 138 12 E + ND 1.58 134 13 F - 38 1.63 146 14 F + 38 1.57 142

1) un amidon cationique non associé à un CPA (cf ESSAIS 3, 5, 7, 9 et 11) ne permet pas, dans les conditions de ces essais, d'obtenir un ensemble de performances totalement satisfaisant, notamment si l'on considère les taux de rétention en amidon (RA) et les indices MULLEN obtenus. En particulier, on n'obtient pas, en absence de CPA, de papier présentant simultanément, outre un bon RA (≥ 50 %), un indice MULLEN au moins égal à 1,65 et un indice CMT 60 au moins égal à 130,

2) un CPA non associé à un amidon cationique (cf ESSAI 2) est totalement inefficace,

3) seuls les amidons cationiques (y compris d'un mélange d'amidons cationiques - cf ESSAI 6) présentant un taux d'azote fixé suffisamment élevé et associés à un CPA (cf ESSAIS 4 et 6), permettent d'obtenir un ensemble de performances satisfaisantes à savoir, outre un bon RA (≥ 50 %, notamment ≥ 60 %), des indices MULLEN et CMT 60 aptes à satisfaire aux exigences de la pratique,

4) la comparaison des résultats obtenus, respectivement, dans le cadre des ESSAIS 8 et 10 (non conformes à l'invention) et dans le cadre des ESSAIS 4 et 6 (conformes à l'invention) montre notamment les avantages apportés par un taux d'azote fixé supérieur à 0,95 % en termes d'indice CMT 60 et/ou d'indice MULLEN. On notera que dans le cas de l'ESSAI 8, la mise en oeuvre du CPA a baissé en outre l'indice MULLEN. En outre, l'ESSAI 10 montre des résultats particulièrement insatisfaisants en termes d'indice MULLEN et de RA, la valeur de ces paramètres étant par ailleurs abaissée de par la présence de PCA,

5) les propositions de l'art antérieur préconisant, de manière très générale et non spécifiquement en association avec un CPA, la mise en oeuvre d'amidons amphotères de type phosphate (cf ESSAI 12) ou de type sulfosuccinate (cf ESSAI 14) ne sont pas entièrement satisfaisantes notamment en termes d'indice MULLEN et de rétention d'amidon. On note d'ailleurs que la mise en oeuvre d'un CPA en association avec de tels amidons amphotères abaisse les performances, déjà moyennes, desdits amidons.

It follows overall from the above results that:

1) a cationic starch not associated with a CPA (cf. TESTS 3, 5, 7, 9 and 11) does not allow, under the conditions of these tests, to obtain a set of completely satisfactory performances, in particular if we consider starch retention rates (RA) and MULLEN indices obtained. In particular, in the absence of a CPA, one does not obtain paper having simultaneously, in addition to a good RA (≥ 50%), a MULLEN index at least equal to 1.65 and a CMT 60 index at least equal to 130,

2) a CPA not associated with a cationic starch (cf. TEST 2) is totally ineffective,

3) only the cationic starches (including a mixture of cationic starches - see TEST 6) having a sufficiently high fixed nitrogen content and associated with a CPA (see TESTS 4 and 6), make it possible to obtain a set satisfactory performance, namely, in addition to a good AR (≥ 50%, in particular ≥ 60%), MULLEN and CMT 60 indices able to meet the requirements of the practice,

4) the comparison of the results obtained, respectively, in the context of TESTS 8 and 10 (not in accordance with the invention) and in the context of TESTS 4 and 6 (in accordance with the invention) shows in particular the advantages provided by a rate fixed nitrogen greater than 0.95% in terms of CMT 60 index and / or MULLEN index. Note that in the case of TEST 8, the implementation of the CPA also lowered the MULLEN index. In addition, TEST 10 shows particularly unsatisfactory results in terms of MULLEN index and RA, the value of these parameters also being lowered by the presence of PCA,

5) the proposals of the prior art advocating, very generally and not specifically in association with a CPA, the use of amphoteric starches of phosphate type (cf. ESSAI 12) or of sulfosuccinate type (cf. ESSAI 14) are not entirely satisfactory, in particular in terms of MULLEN index and starch retention. It should also be noted that the implementation of a CPA in association with such amphoteric starches lowers the performance, already average, of said starches.

The above findings show the advantages manufacturers brought by the manufacturing process according to the invention, which allows, inter alia, by the physical characteristics which it confers on the paper obtained, delete, if necessary, the subsequent operations of surface treatment of paper, the disadvantages of which terms of cost, machine speed and productivity have been recalled previously.

EXAMPLE 2

Furthermore, the Applicant Company globally confirmed, on TECHPAP form, the interest of the object process of the invention, in particular in terms of starch retention and / or chemical characteristics of the paper, in the circumstances defined below.

* TEST 15:

• fibrous composition: identical to the pulp tested at TEST 1 to 14 ("PASTE 1"),
• starches used: 1% starch type A + 1% of anionic starch of the VECTOR R A180 type sold by the Applicant,
• CPA implemented: 2% of "PAC 18",
• starch contact time A: 5 min,
• contact time PAC 18: 6 min,
• contact time VECTOR ^R A180: 1 min,
• paper weight: 123 g / m2.

Under these conditions, a MULLEN index of 1.71 and a CMT 60 index of 137.

* TEST 16:

• fibrous composition: PATE 1,
• starch used: 2% starch A in the form uncooked starch powder,
• CPA implemented: 2% of "PAC" 18,
• starch contact time A: 6 min, with heating 10 min prior to 45 ° C in order to dissolve the starch,
• PAC 18 contact time: 6 min,
• paper weight: 127 g / m ² .

Under these conditions, completely satisfactory physical characteristics (of which u22n CMT 60 index of 136) and, in addition, a rate of exceptional starch retention for such a type of fibrous composition, i.e. greater than 90%. This essay shows that it is possible, within the framework of the invention, to put using an uncooked starch, a fortiori pregelatinized, from when the operating conditions, upstream and / or at even level of the dough, ensure the setting contact between cationic starch and CPA at a temperature adequate, for example from 20 to 50 ° C (in the case present: 45 ° C), conditions which are practically used at some paper mills. We can thus get rid of the implementation of a conventional, continuous or discontinuous.

* TEST 17:

• fibrous composition: paste reconstituted from thick pulp made from old paper with a pH 7.0, a total concentration of 7.17 g / l, a soluble concentration of 3.32 g / l and a resistivity of 457 ohms,
• starch used: 2% starch A,
• CPA used: 1% polychlorosulfate basic aluminum type "WAC",
• starch contact time A: 4 min 30,
• WAK contact time: 5 min
• paper weight: 135 g / m ² .

We obtain, under these conditions (composition fibrous different from PATE 1, in particular) a clue MULLEN (value: 1.80) and a starch retention rate (value: 95%) particularly high.

Claims (12)

1. Process for the manufacture of paper from a fibrous composition, characterized in that the said fibrous composition is brought into contact, simultaneously or non-simultaneously, with at least one cationic starch exhibiting a level of fixed nitrogen greater than 0.95 %, expressed with respect to the dry weight of starch, and with at least one polyaluminium compound.
2. Process according to Claim 1, characterized in that the cationic starch exhibits a level of fixed nitrogen of approximately 1.0 % to approximately 3.0 %, preferably of 1.0 % to 2.5 % and more preferentially still between 1.0 % and 1.6 %.
3. Process according to either of Claims 1 and 2, characterized in that the starch is in the form of an uncooked starch powder or of a pregelatinized starch powder when it is brought into contact with the fibrous composition, the said fibrous composition preferably exhibiting a temperature of approximately 25°C to approximately 50°C.
4. Process according to one of Claims 1 to 3, characterized in that the polyaluminium compound is an aluminium polyhydroxide, an aluminium polychloride, a basic aluminium polychloride, a basic aluminium polychlorosulphate or an aluminium polysulphate, the said polyaluminium compound preferably exhibiting an aluminium content, expressed as Al₂O₃, of approximately 8 % to approximately 20 % by weight and more preferentially of 10 to 18 % by weight.
5. Process according to one of Claims 1 to 4, characterized:

   in that the cationic starch is brought into contact with the fibrous composition between a point corresponding to the refiner and a point lying just before the head box, preferably between a point lying just after the refiner and a point lying just before the mixing pump of the paper machine, and

   in that the polyaluminium compound is brought into contact with the fibrous composition between a point corresponding to the refiner and a point corresponding to the head box and/or to the white waters, preferably between a point lying just after the refiner and a point lying just before the head box of the paper machine.
6. Process according to one of Claims 1 to 5, characterized in that the time period between bringing either the cationic starch or the polyaluminium compound respectively into contact with the fibrous composition and bringing either the polyaluminium compound or the cationic starch respectively into contact with the fibrous composition is between 0 and 60 minutes, preferably between 0 and 45 minutes and more preferentially still between 10 seconds and 40 minutes.
7. Process according to one of Claims 1 to 6, characterized in that the paper obtained is not subjected, on either of its two faces or indeed on both its two faces, to any surface treatment employing a native or physically and/or chemically modified starch.
8. Process according to one of Claims 1 to 7, characterized in that the paper obtained is a paper for graphical use or a paper for wrapping or packaging, in particular a fluting paper or a liner paper for corrugated fibreboard.
9. Process according to one of Claims 1 to 8, characterized in that the fibrous composition exhibits a pH, controlled or uncontrolled, lying between approximately 6.0 and approximately 8.0 and preferentially between 6.1 and 7.1.
10. Process according to one of Claims 1 to 9, characterized in that the fibrous composition is brought into contact, at any time whatever before the formation of the sheet, with at least one silicic or aluminosilicic compound, in particular with a colloidal silicic acid, the particles of which have a specific surface of approximately 50 to approximately 1000 m²/g, and optionally with at least one filler or one sizing agent.
11. Fluting paper for corrugated fibreboard which is not surface-treated and which has a substance of 120 to 130 g/m², obtainable by the process according to one of Claims 1 to 10, characterized in that it exhibits:

    a CMT 60 value of at least approximately 130, preferably of at least approximately 135, expressed as N, and

    a Mullen value of at least approximately 1.65, preferably of at least approximately 1.70, expressed as Kpa/g/m².
12. Use of a cationic starch exhibiting a level of fixed nitrogen greater than 0.95 % expressed with respect to the dry weight of starch and of a polyaluminium compound for the manufacture of paper, in particular paper for graphical use or paper for wrapping or packaging and very particularly fluting paper for corrugated fibreboard or liner paper for corrugated fibreboard.