EP0282415B2 - Process for producing paper - Google Patents

Abstract

Process characterised in that one (or more) cationic starch(es) and one (or more) anionic starch(es) other than a starch phosphate are introduced, separately from each other, at two or more points (8, 12, 13, 14), especially at the wet end, into the fibre composition forming the raw material. <IMAGE>

Description

The subject of the invention is a manufacturing process paper, the term "paper" denoting in what follows any flat structure or sheet based on cellulosic fibers - most frequently used raw material in the paper and cardboard industry-- from a raw material consisting of a fibrous composition containing pulp from cellulosic fibers of recovery or recycled pasta.

The well-known use of cationic starches which are introduced into the fiber mass before the leaf formation, increased retention 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 or cationicity, increases the number of connections between fibers as well as between fibers and fillers, resulting in resistance larger paper: and thanks to this larger resistance of the paper, it became possible to decrease the concentration of the fiber mass or to resort to lower quality fibers.

It turns out that the benefits of implementation of cationic starches do not allow always, for a few years, to compensate for the disadvantages growing created by the increasing degradation of the quality of raw materials.

Indeed, to face profitability concerns increasingly strict economic, not only the semi-chemical paste traditionally used for example for making paper for corrugated board saw its reduced share in favor of pulp from recovered cellulose fibers, commonly called FCR, but moreover the very quality of these FCRs is more and more mediocre due to the increasing number of recycling "old paper".

Added to this is the fact that in paper machines, the trend is more and more towards closure systematic circuits, resulting in enrichment of production water with organic and mineral materials. These factors contribute to the decrease in the strength of the paper; the proportion of cationic starches that can be fixed on the fibers decreases, hence a lower resistance of the sheet.

Various solutions have been proposed to remedy these drawbacks.

Thus, we have developed starches characterized by an increasing cationicity, but well obviously limited by the maximum cationicity which the daisical processes for obtaining cationic starches. And, in any case, whatever the degree of cationicity, the closing of the circuits and the deterioration in the quality of the fibers results in an inevitable drop in the resistance of the papers.

Knowing that the effectiveness of a cationic starch is all the greater as its probability of fixation on fiber is important, we used (see US Patent 4,066,495) to increase this probability of fixation to associations such as "cationic starch - polyacrylamide" or "cationic starch - alumina sulfate or poly aluminum chloride ".

This use of two or more compounds of the same ionicity has in fact the sole objective of increasing the retention of fillers and fibers without changing the composition of the paper.

In the same vein, we appealed (see FR 1,499,781) to starches containing both cationic groups and anionic phosphate groups.

These starches, although consequently comprising groups of different ionicity, nevertheless have a essentially cationic in character, therefore implying their own usage limits.

Successive application of starch phosphate and a cationic starch - known from the document "Ecological aspects of employment starch derivatives ", Paper, Cardboard and Cellulose, 1975, 24 (12), pages 56-62-- only improves the resistance of the paper obtained and this in a proportion insufficient. In addition, these phosphate starches contribute to increase the polluting load by the presence of nitrogen compounds from their manufacturing process.

In so-called "dual" techniques, this is not starches having both cationic groups and phosphate groups or the use of phosphates of cationic starches that we had recourse, but to associations of cationic starches and of compounds of different ionicity.

Thus (see EP 41.056), we used starches cationic in combination with colloidal silicic acid; moreover, patent EP 60,291 describes the preparation a gel based on cationic starch and carboxy-methylcellulose or a uronic acid polymer, this gel being partially dehydrated by the action of a solution colloidal of polysilicic acid or an oxypolyaluminum compound.

Dual techniques lead to improvement retention, allowing the manufacture of a paper with higher filler content. They allow substantial cellulose savings but are not applicable in all cases. In addition, the amount of starch attached to cellulose at the time of formation of the leaf still limited, physical characteristics paper thus obtained is not always improved enough.

To obtain a paper with characteristics increased mechanical forces, it is therefore necessary to subject the paper produced using one of the techniques previous, a surface treatment carried out in particular in a machine of the "size-press" type; such treatment increases the proportion of starch 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" results in elsewhere a significant decrease, of the order of 15 to 20% of the speed of the machines and therefore of the production of paper.

It follows from the above that none of the processes existing leads, with a satisfactory cost price, obtaining paper with the characteristics desired.

The object of the invention is therefore, above all, to provide a paper-making process that responds better than those that already exist at the various desiderata of the convenient.

This incumbent company noted at the end extensive research that it became possible, including under conditions deemed difficult, that is to say in the case where the raw material is degraded, i.e. consisting of a fibrous composition comprising pulp from recovered cellulosic fibers or recycled pasta, to increase significantly, that is to say at least 30%, even 50% or even more than 100%, the limit threshold for fixing starch in the composition fibrous when we introduce into the mass of fibers, in particular partly wet, separately one of the other, a cationic starch and another anionic starch than a starch phosphate.

We denote by the expression "limit threshold of fixation of starch in the fibrous composition "the amount of starch fixed per unit weight of composition dry fibrous, the latter comprising all of the insoluble constituents used to form the sheet of paper.

It follows that the papermaking process, in an installation with a wet part, from of a raw material constituted by a composition fibrous with pulp from cellulosic fibers recovery or recycled pulp, according to which introduced into said fibrous composition, in two or several points of the installation located in particular in the wet part of it, separately from each other, of 0.2 to 5% of one or more cationic starches and 0.2 to 5% of one or more anionic starches chosen from the group consisting of starch sulfates, starch sulfocarboxyls and starch carboxyalkyls, these percentages being expressed as dry starch relative to the dry fibrous composition, the proportion of starch cationic with respect to anionic starch being understood between 10/1 and 1/10, these ratios being expressed in dry weight of starch.

According to an advantageous embodiment of the above process, anionic starch is selected from the group including carboxymethylated starches, starches succinylated, starch sulfosuccinates, starches sulfated. In the following, the expression "anionic starch" means all products of this type, excluding starch phosphates.

Preferably, the amounts of cationic starch and anionic are between 0.4% and 3%, more preferably between 0.7 and 2.5%, the percentages being expressed as dry starch relative to the composition dry fibrous.

Cationic and anionic starches are advantageously introduced into the fibrous composition in the form diluted aqueous glue with a concentration of less than 5%, preferably less than 3% and, more preferably, less than 1%, the lower limit being 0.01%.

Preparation of adhesives (if the starch used is not not directly soluble in cold water, in which case a simple dispersion in water is sufficient) is carried out in a manner known per se, by discontinuous or continuous cooking, for example in a continuous pressure cooker suitable for ensuring dosing, cooking and dilution.

According to an advantageous embodiment of the invention, it can be proposed for the sake of simplification of the process in question to use starches anionic or cationic directly soluble in cold water and introduce them, in powder form, directly into the fibrous suspension.

According to another advantageous embodiment of the process according to the invention, the proportion of starch cationic versus anionic starch must be understood between 5/1 and 1/3 and, preferably, between 3/1 and 1/2, these ratios being expressed in dry weight of starch.

The point of introduction of cationic starches and anionic is defined according to the physico-chemical characteristics of the system, this choice resulting in different values of the contact time with the composition fibrous.

Optimal concentrations of cationic starch and in anionic starch used in accordance with the invention, that is to say those allowing to obtain the best performance, are determined inside limits indicated, depending in particular on the mass of fibers used, and of the aqueous medium used (environment ionic) or characteristics specific to each paper machine.

Within these limits, performance inherent in the invention as measured for example a using the starch retention test, are higher to those that could be expected by simple addition individual job performance respectively cationic starch or anionic starch, therefore reflecting a synergistic effect.

The cationic starches used in accordance with the invention are selected from those having an electronic acceptor state, obtained using substituent groups of an electropositive nature, called cationic.

The most commonly used substituents are those containing a tertiary or quaternary nitrogen atom, although the phosphonium and sulfonium groups can also be used.

   et

dans lesquelles

• A représente les groupements :
  
• X représentant dans les susdites formules un atome d'halogène, tel que par exemple le chlore,
• R₁ et R₂ représentent chacun, indépendamment l'un de l'autre, un radical alkyle à chaíne droite ou ramifiée en C₁-C₄ ou bien sont réunis en une structure cydique,
• R₃ représente un radical alkyle à chaíne droite ou ramifiée en C₁-C₄ et n représente un nombre entier de 1 à 3.

As reactants for cationization of starch, halohydrins or epoxides corresponding to the following formulas can be used:

and

in which

• A represents the groups:
  
• X representing in the above formulas a halogen atom, such as for example chlorine,
• R ₁ and R ₂ each represent, independently of one another, a straight chain or branched C ₁ -C ₄ alkyl radical or else are combined in a cydic structure,
• R ₃ represents a straight chain or branched C ₁ -C ₄ alkyl radical and n represents an integer from 1 to 3.

• le diéthylamino chloroéthane,
• le chlorure de triméthylammonium époxypropyle,
• le chlorure de triméthylammonium chloro-1-hydroxy-2-propane.

The cationization reagents used are preferably:

• diethylamino chloroethane,
• epoxypropyl trimethylammonium chloride,
• trimethylammonium chloride chloro-1-hydroxy-2-propane.

The electrophilic power of these starches is quantified by measuring the degree of substitution (DS), i.e. the number of hydroxyl functions which have been substituted by elementary glucosidic unit. In good standing general, the DS is at most equal to 0.3; it is preferably between 0.02 and 0.20 and, more preferably, between 0.04 and 0.15.

• dans le cas des phosphonates d'amidon, l'acide diéthylphosphonique aminochloréthane.
• dans le cas des sulfates d'amidon, l'acide sulfamique, les sulfamates ou encore les complexes SO₃- donneurs d'électrons tels que le SO₃-TMA (triméthylamine), le SO₃-pyridine,
• dans le cas des sulfoalkyles d'amidon, les 2-chloroéthane-sulfonates et le 3-chloro-2-hydroxypropane-sulfonate,
• dans le cas des carboxyalkyles d'amidon, les sels d'acides halo-1-carboxyliques tels que le monochloracétate de sodium ou le chloropropionate de sodium, les lactones comme la propiono- ou butyrolactone, l'acrylonitrile (réaction suivie d'une saponification), les anhydrides d'acides tels que les anhydrides maléique, succinique, phtalique et autres,
• dans le cas des sulfocarboxyles d'amidon, l'acide chloro-3-sulfo-2-propionique.

For the preparation of the anionic starches used in accordance with the invention, the anionic substituents are introduced into the starch molecule using functional reagents, preferably:

• in the case of starch phosphonates, diethylphosphonic acid aminochlorethane.
• in the case of starch sulfates, sulfamic acid, sulfamates or alternatively the SO ₃ - electron donor complexes such as SO ₃ -TMA (trimethylamine), SO ₃ -pyridine,
• in the case of starch sulfoalkyls, 2-chloroethane sulfonates and 3-chloro-2-hydroxypropane sulfonate,
• in the case of starch carboxyalkyls, the salts of halo-1-carboxylic acids such as sodium monochloroacetate or sodium chloropropionate, lactones such as propiono- or butyrolactone, acrylonitrile (reaction followed by saponification ), acid anhydrides such as maleic, succinic, phthalic and other anhydrides,
• in the case of starch sulfocarboxyls, chloro-3-sulfo-2-propionic acid.

Although the strength of the nucleophilic power of the starches contains anionic groups should, in theory, being specified by the value of pKA, the DS is measured in practice.

The maximum value that the DS can reach is equal to 3. However, as a general rule, we will retain, for the anionic products targeted by the invention, a DS at most equal to 1.5 and, preferably, at most equal to 0.5.

• "Starch : Chemistry and Technology", édité par Whistler et al, vol. II (Industrial aspects), 1967, Academic Press;
• "Starch Production Technology", édité par J.A. Radley, 1976, Applied Science Publishers Ltd. London ;
• "Starch : Chemistry and Technology", édité par Whistler et al, 2ème édition (1984), Academic Press, Inc., pages 354-385].
  Dans l'état actuel de la technique, la réaction peut se dérouler en phase humide, c'est-à-dire sur une suspension d'amidon, en milieu aqueux ou en milieu solvant, mais également en phase sèche, en présence d'un catalyseur de nature alcaline. On choisira de préférence la phase solvant ou la phase sèche dans le cas où la solubilité dans l'eau devient importante quand le DS croít. La fixation peut également être effectuée lors de la solubilisation de l'amidon dans les conditions susdécrites.

The attachment to starch of a reagent carrying a cationic or anionic group is well known [see:

• "Starch: Chemistry and Technology", edited by Whistler et al, vol. II (Industrial aspects), 1967, Academic Press;
• "Starch Production Technology", edited by JA Radley, 1976, Applied Science Publishers Ltd. London;
• "Starch: Chemistry and Technology", edited by Whistler et al, 2nd edition (1984), Academic Press, Inc., pages 354-385].
  In the current state of the art, the reaction can take place in the wet phase, that is to say on a starch suspension, in an aqueous medium or in a solvent medium, but also in the dry phase, in the presence of an alkaline catalyst. The solvent phase or the dry phase will preferably be chosen in the case where the solubility in water becomes high when the DS increases. The fixing can also be carried out during the solubilization of the starch under the conditions described above.

The binding reactions on the starch of these cationic or anionic groups were carried out and described with starches from all sources such as corn, rice, wheat, potato, cassava and others. They can, according to an advantageous embodiment of the invention, be carried out on starches having previously undergone more or less extensive crosslinking treatment. This treatment gives anionic or cationic starches thus obtained special properties resulting in greater freedom as to the choice of their point of introduction during their implementation in the context of the invention.

In a preferred embodiment of the invention, the present titular Company was able to observe, at level of anionic starches and cationic starches used, differences in behavior more or less visible, depending in particular on the cellulose pastes and the aqueous media used.

It is generally the cationic potato starch which is recognized as providing the best performances. Particular preference is given to anionic starches belonging to the group of sulfocarboxyalkyl derivatives.

The remarkable colloidal properties of the starches used in accordance with the invention have important repercussions on papermaking, for example improving the retention of fines from cellulose and fillers when making the sheet and the speed of water dripping through the sheet.

In the context of the process according to the invention, other additives may also be used, such as for example flocculating agents traditionally used in stationery such as, for example, sulfate alumina, polychloride of Al, polyethyleneimine, polyacrylamide and others.

Finally, the invention can be better understood using the examples which follow and which are either comparative, either relating to advantageous embodiments.

To evaluate the results obtained by implementing the method according to the invention, use is made of a facility capable of reproducing at least certain steps in the production of paper from cellulose fibers and shown schematically in the single figure.

The installation in question comprises a vat 1 inside which the composition comprising a mass of fibers which is suspended and homogenized using an agitator 2. Agitation is maintained throughout the duration of the test so as to ensure perfect regularity of supply to the circuit. She is however sufficiently weak not to modify in time the state of refinement of the composition fibrous studied and not to degrade the flocs.

Once prepared, the fibrous composition is conveyed by a pipe 3 equipped with a pump P ₁ in a transit vat 4 provided with an agitator 5 and in which it can be maintained for a predetermined time to allow contact with one or more several of the adjuvants used at this stage; it is also possible not to plan any stay in the vat room 4; in this case, the fibrous composition simply crosses the vat and is brought by a pipe 6 directly to a pump P ₂ located at the outlet of the vat 4.

In all cases, the fibrous composition will be drawn from the vat 1 with a rigorously constant flow.

Downstream of the pump P ₁ , the pipe 3 is equipped with an enclosure 7 inside which it is possible to adjust the pH of the fiber suspension by adding alkali or acid; and downstream of the enclosure 7, the pipe 3 comprises an element schematically shown at 8 and suitable for allowing the introduction of one or more adjuvants into the fibrous composition.

The pump P ₂ routes the suspension of fibers by a line 9 to two mixers in series respectively M ₁ and M ₂ equipped with agitators respectively 10 and 11; the adjustment of the rotational speeds and the shape of the blades of the agitators 10 and 11 are chosen so that the conditions prevailing inside the mixers are as close as possible to the shear conditions existing in the wet part of an industrial circuit of paper making.

Three elements schematically shown in 12, 13 and 14 and suitable for allowing the introduction of adjuvants into the fibrous composition are arranged on the line 9 at the outlet of the pump P ₂ for the first and respectively before the inlet of the mixers M ₁ and M ₂ for the other two; these elements make it possible to choose the order of introduction, the shearing conditions before or after addition and the contact times between the adjuvants and the fibrous composition.

• TAPPI, Octobre 1973, Volume 56, n° 10, p. 46-50
• TAPPI, Février 1976, Volume 59, n° 02, p. 67-70
• TAPPI, Juillet 1977, Volume 60, n° 07, p. 110-112
• TAPPI, Novembre 1978, Volume 61, n° 11, p. 108-110
  (TAPPI = Technical Association of the Pulp and Paper Industry) et propre à simuler l'égouttage de la pâte à papier sur la toile d'une machine à papier.

The second mixer M ₂ is connected by a pipe 15 to a measuring device 16 called "Britt-Jar" in the art, described in the following publications:

• TAPPI, October 1973, Volume 56, n ° 10, p. 46-50
• TAPPI, February 1976, Volume 59, n ° 02, p. 67-70
• TAPPI, July 1977, Volume 60, n ° 07, p. 110-112
• TAPPI, November 1978, Volume 61, n ° 11, p. 108-110
  (TAPPI = Technical Association of the Pulp and Paper Industry) and suitable for simulating the drainage of paper pulp on the canvas of a paper machine.

At the exit of the "Britt-Jar", we recover in an enclosure 17 draining water which can be assimilated to what is called "water under canvas" in the technique of papermaking, expression used in the following.

• pour une partie, rejetées à l'égout par une canalisation 18,
• pour une autre partie, recyclées par une canalisation 19 équipée d'une pompe P₃ vers la canalisation 9 en un point 20 situé entre les éléments 12 et 13.

The canvas water recovered in enclosure 17 is

• for a part, discharged to the sewer by line 18,
• for another part, recycled through a pipe 19 fitted with a pump P ₃ to the pipe 9 at a point 20 located between the elements 12 and 13.

The enclosure 17 is also connected to a secondary circuit making it possible to bring a third part of the water under canvas contained in said enclosure via a pipe 21 equipped with a pump P ₄ to a tubidimeter 22 at the outlet of which the waters under canvas which have passed through it are brought back to enclosure 17 by a pipe 23.

Perfect homogenization of the canvas water is ensured in this secondary circuit.

The turbidimeter 22 makes it possible to assess the content of water under canvas in mineral and organic matter (fibers, fillers and others); it turns out that the measurements carried out continuously using this device are directly related to retention and more or less proportional to the amount of soluble matter and insoluble materials present in canvas waters.

We also use a photometer which can be that known under the brand NANOCOLOR 50D (manufactured by the Macherey-Nagel Company, 5160-Duren, R.F.A., and marketed by the Techmation Company, 20 Quai de la Marne, 75019 Paris), and which allows measurements to be made reflecting the overall level of fixation starches; the principle of these measurements is based on the expression of the difference between the measurement carried out on a supernatant freed by a few minutes of rest of the cellulosic fibers and fillers, and colored with iodine, and that performed on the same uncoloured supernatant.

EXAMPLE 1

• 35% de pâte à la soude - fibres longues,
• 35% de pâte à la soude - fibres courtes,
• 15% de "cassés couchés" (c'est-à-dire de pâtes recyclées) chargés au carbonate de calcium,
• 15% de "cassés couchés" chargés au kaolin.

For a first series of tests, a pulp of the so-called "acid medium" type was prepared from cellulosic fibers using the following main constituents:

• 35% soda ash - long fibers,
• 35% soda ash - short fibers,
• 15% of "coated broken" (that is to say recycled pasta) loaded with calcium carbonate,
• 15% of "coated broken" loaded with kaolin.

• 35% de kaolin (grade G),
• 4% de sulfate d'alumine.

After refining the resulting mixture into potable water at 48 ° SR (Schopper-Riegler degree, AFNOR standard NF Q 50-003), the following were introduced:

• 35% kaolin (grade G),
• 4% alumina sulfate.

• concentration de la pâte avant introduction des charges (kaolin et sulfate d'alumine) : 8 glkg,
• concentration de la pâte chargée : 10,6 glkg
• pH 4,7 (en cuvier)
• résistivité : 623 Ω-cm
• acidité : 140 mg/l (compté en acide sulfurique).

The fibrous composition or pulp thus prepared had the following characteristics:

• concentration of the dough before introduction of the charges (kaolin and alumina sulfate): 8 glkg,
• concentration of loaded dough: 10.6 glkg
• pH 4.7 (in vat room)
• resistivity: 623 Ω-cm
• acidity: 140 mg / l (counted as sulfuric acid).

The acidity was measured by simple assay from an N / 10 sodium solution with, for colored indicator, phenolphthalein.

Several experiments were carried out by treating this paste with a cationic starch and then using a anionic starch.

As cationic starch, a cationic potato starch with a nitrogen content was used. fixed on dry between 0.55 and 0.60% (which corresponds to a DS between 0.063 and 0.069); it's about in this case that marketed by the licensee under the brand HI-CAT® 180.

• lait à 10% de matière commerciale
• température : 120°C, sous une pression suffisante pour que la cuisson ait lieu en phase liquide,
• temps de maintien : 30 secondes,
• dilution en ligne par l'eau froide pour amener la lecture réfractométrique à moins de 0,5%.

For its implementation, this cationic starch was dissolved on a continuous cooking appliance, under the following conditions:

• 10% commercial milk
• temperature: 120 ° C, under sufficient pressure for cooking to take place in the liquid phase,
• hold time: 30 seconds,
• online dilution with cold water to bring the refractometric reading to less than 0.5%.

• un sulfosuccinate de fécule présentant un DS de 0,05 (en l'occurrence celui commercialisé par la Société Demanderesse sous la marque VECTOR® A 180),
• une fécule sulfatée présentant un DS de 0,087, référencée AS,
• une fécule phosphatée d'un DS d'environ 0,04 (en l'occurrence celle commercialisée par la Société AVEBE sous la marque RETABOND AP).

As anionic starches, those identified below were used:

• a starch sulfosuccinate having a DS of 0.05 (in this case that marketed by the Applicant Company under the brand VECTOR® A 180),
• a sulphated starch with a DS of 0.087, referenced AS,
• a phosphate starch with a DS of approximately 0.04 (in this case that marketed by AVEBE under the brand RETABOND AP).

• lait à 4% de matière commerciale
• maintien pendant 5 minutes à 95-98°C
• dilution en ligne par de l'eau froide pour amener la lecture réfractométrique à 2%.

The anionic starches studied were prepared by steaming in an open tank under the following conditions:

• milk with 4% commercial matter
• hold for 5 minutes at 95-98 ° C
• online dilution with cold water to bring the refractometric reading to 2%.

The installation described above has been used in connection with the single figure.

• les vitesses de rotation des mélangeurs M₁ et M₂ étaient respectivement de 1000 et 2000 tours par minute,
• les débits des pompes P₁, P₂ et P₃ (retour des eaux sous toile) étaient de 400 millilitres par minute),
• réglage du turbidimètre : amplificateur variable × 5.

The operating parameters of the installation have been defined as follows:

• the rotational speeds of the mixers M ₁ and M ₂ were respectively 1000 and 2000 revolutions per minute,
• the flow rates of pumps P ₁ , P ₂ and P ₃ (return of the water under canvas) were 400 milliliters per minute),
• turbidimeter setting: variable amplifier × 5.

The respective points of introduction of the cationic starch and the anionic starches studied were arbitrarily choose.

HI-CAT® 180 cationic starch is introduced through element 8, resulting in a contact time of 5 minutes before going to "Britt-Jar".

The anionic starches are introduced by element 12, hence a contact time of 30 seconds before the passage on "Britt-Jar".

The amount of cationic starch used is 1% dry relative to the dry fibrous composition.

For anionic derivatives, the quantity fixed is that allowing the lowest turbidimetric reading.

ESSAI 1: Témoin (sans amidon)

ESSAI 2 : HI-CAT® 180 seul (1%)

ESSAI 3 : HI-CAT® 180 (1%) ; VECTOR® A 180 (1,5%)

ESSAI 4 : HI-CAT® 180 (1%) ; AS (1,6%)

ESSAI 5 : HI-CAT® 180 (1%) ; RETABOND AP (0,65%).

The number of experiments carried out is five, namely:

TEST 1: Control (without starch)

TEST 2: HI-CAT® 180 alone (1%)

TEST 3: HI-CAT® 180 (1%); VECTOR® A 180 (1.5%)

TEST 4: HI-CAT® 180 (1%); AS (1.6%)

TEST 5: HI-CAT® 180 (1%); RETABOND AP (0.65%).

• mesure de la turbidité des eaux sous toile,
• évaluation de la proportion globale d'amidon fixé à l'aide du photomètre,
• mesure de la quantité de fibres et charges retenues, communément désignée par "rétention toile",
• mesure de la rétention des charges.

The measurements are as follows:

• measurement of the turbidity of the water under canvas,
• evaluation of the overall proportion of starch fixed using the photometer,
• measurement of the quantity of fibers and fillers retained, commonly known as "canvas retention",
• charge retention measurement.

We express "canvas retention" by the ratio

We express the retention of charges by the ratio

The results of these measurements are collated in Table I. Essays Turbidity (water under canvas) Photometer reading (starch) Canvas retention% Load retention% 1 66.5 0.071 80.6 68.2 2 70.5 0.186 79.2 66.7 3 23.5 0.208 94 82.7 4 41 0.157 86.45 74.4 5 63.5 0.583 79.3 65.7 pH: 4.4 - 4.5 (H ₂ SO ₄ )

The results presented in Table I show that the sequential introduction of anionic starch from sulfated type and more particularly of the sulfosuccinate and cationic starch type makes it possible to increase significantly retention of fibers and fillers while ensuring perfect fixation of materials starch used.

This fixation of starches is all the more remarkable as the concentration of starches used in tests 3 and 4 is at least twice that introduced in test 2.

On the other hand, it can be seen that the results obtained in the presence of phosphate starches are clearly less satisfactory, in particular from the point of view of starch fixation (see photometric reading) and retention of charges.

EXAMPLE 2

• concentration totale : 12,25 g/l,
• concentration en matières solubles : 3,7 g/l,
• pH : 6,10,
• résistivité : 438 Ω-cm,
• dureté : 174° TH,
• amidon dans le filtrat : inférieur à 0,1 g/l,
• calcium soluble : 575 mg/l,
• aluminium soluble : 2 mg/l,
• cendres à 900°C : 2,2 mg/l.

For this second series of tests, a thick paste of the so-called "acid medium" type, based on waste paper, was removed from an industrial machine, which, diluted with clarified water from the same factory, provided an introduced paste. in the vat room and whose characteristics were as follows:

• total concentration: 12.25 g / l,
• soluble matter concentration: 3.7 g / l,
• pH: 6.10,
• resistivity: 438 Ω-cm,
• hardness: 174 ° TH,
• starch in the filtrate: less than 0.1 g / l,
• soluble calcium: 575 mg / l,
• soluble aluminum: 2 mg / l,
• ash at 900 ° C: 2.2 mg / l.

In this series of tests, the cationic starch used is that of Example 1, prepared in the same conditions.

• lait à 5% de matière commerciale,
• maintien pendant 5 minutes à 95-98°C,
• dilution en ligne par de l'eau froide pour amener la lecture réfractométrique à 2%.

The anionic starch used is the sulphate starch of Example 1. It is prepared by steaming in an open tank under the following conditions:

• milk with 5% commercial matter,
• hold for 5 minutes at 95-98 ° C,
• online dilution with cold water to bring the refractometric reading to 2%.

The installation is that of the single figure.

• mélangeur M₁ : agitation à 1000 tours/minute,
• mélangeur M₂ : agitation à 2000 tours/minute,
• les débits des pompes P₁ et P2 sont de 500 millilitres par minute,
• le débit de la pompe P3 est de 400 millilitres par minute, l'excédent étant rejeté par la canalisation 18,
• le pH a été maintenu à 5,7 avec de l'acide sulfurique dilué, introduit dans les eaux sous toile amenées pour la dilution.

The operating parameters of the installation have been defined as follows:

• mixer M ₁ : stirring at 1000 revolutions / minute,
• mixer M ₂ : stirring at 2000 rpm,
• the flow rates of the pumps P ₁ and P2 are 500 milliliters per minute,
• the flow rate of the pump P3 is 400 milliliters per minute, the excess being discharged through line 18,
• the pH was maintained at 5.7 with dilute sulfuric acid, introduced into the canvas water supplied for dilution.

• l'amidon cationique a été introduit par l'élément 8 (temps de contact de 10 minutes) et une quantité complémentaire a, dans certains essais, été introduite par l'élément 14,
• l'amidon anionique a été introduit par l'élément 12.

The respective points of introduction of the cationic starch and of the anionic starch were chosen as follows:

• the cationic starch was introduced by element 8 (contact time of 10 minutes) and an additional quantity was, in certain tests, was introduced by element 14,
• anionic starch was introduced by element 12.

The amounts of cationic starch and anionic starch and the point of introduction are indicated in Table II. Test Quantity introduced by element 8 Quantity introduced by element 14 Quantity introduced by element 12 6 (witness) 7 1% HI-CAT 180 0.5% HI-CAT 180 8 1.5% HI-CAT 180 0.5% HI-CAT 180 9 2.5% HI-CAT 180 0.5% HI-CAT 180 10 2% HI-CAT 180 1% AS 11 2% HI-CAT 180 1.5% AS

The amounts of cationic and anionic starch are expressed on a dry basis relative to the fibrous composition dryer contained in the vat room 1.

The measurements carried out are those of the turbidity of the water under canvas, the web retention and the quantity starch (in mg / l) found in water under canvas determined by enzymatic assay.

The results are collated in Table III. Test Turbidity (water under canvas) Canvas retention Starch (canvas water, mg / l) 6 (witness) 93 79.6 60.9 7 99 79.5 73.7 8 110 78.6 97.8 9 120 78.6 151.2 10 102 80.4 85.3 11 106 80.7 98.1 The pH of the canvas water is 5.7 to 5.8.

• la limite de fixation correcte de l'amidon cationique utilisé, introduit en deux points comme précisé plus haut, se situe vers 2% (voir essai 8),
• quand on utilise successivement des amidons cationique et anionique, on peut atteindre, pour des résultats équivalents, des taux d'amidon de l'ordre de 3,5% ; le gain en rétention peut alors être de 3 points, ce qui, dans le système utilisé, est important.

In light of these results, it can be seen that

• the limit for the correct fixation of the cationic starch used, introduced at two points as specified above, is around 2% (see test 8),
• when cationic and anionic starches are used successively, it is possible to achieve, for equivalent results, starch levels of the order of 3.5%; the retention gain can then be 3 points, which in the system used is important.

As an additional experiment, the fibrous composition was taken after the second mixer, instead of carrying out the measurements on "Britt-Jar" and "formettes" (sheets of paper) of a grammage were prepared. approximately 150 g / m ² using this paste using the RAPID-KOETHEN type material marketed for example by the company Enrico Toniolo SpA (Milan, Italy) and well known to those skilled in the art.

Since the pulp studied is essentially intended for fluting paper, the CMT 60, that is to say the Concora index (see standard TAPPI T 809 su 66), was measured, the results being collated in Table IV. Test CMT 60 (Newtons) 6 151 7 183 8 196 9 193 10 188 11 222

We can see from these results that the gain in CMT is roughly proportional to the quantity fixed transformed starch. The use of 2% cationic starch increases the CMT by 45 N (test 8). The overall use of 3.5% transformed starch (test 11) allows an overall gain of 71 N, which constitutes a decisive advantage of the process according to the invention.

EXAMPLE 3

In this example, the cationicity of the starch is varied.

A thick pulp obtained from old paper was taken on an industrial machine, then diluted with the water under canvas coming from the same machine to constitute the fibrous composition intended for supply the installation according to the single figure.

• concentration totale :   16,5 g/l
• concentration en matières solubles :   4,8 g/l
• pH :   5,7
• acidité : 253 mg/l compté en acide sulfurique
• résistivité :   338 Ω - cm
• aluminium soluble :   3 mg/l.
• sodium soluble :   310 mg/l
• calcium soluble :   650 mg/l
• magnésium soluble :   24 mg/l
• amidon :   0,39 g/l
• sucres réducteurs :   0,12 g/l
• cendres à 900°C :   2,8 g/l.

Analysis of said composition leads to the following values:

• total concentration: 16.5 g / l
• soluble matter concentration: 4.8 g / l
• pH: 5.7
• acidity: 253 mg / l counted as sulfuric acid
• resistivity: 338 Ω - cm
• soluble aluminum: 3 mg / l.
• soluble sodium: 310 mg / l
• soluble calcium: 650 mg / l
• soluble magnesium: 24 mg / l
• starch: 0.39 g / l
• reducing sugars: 0.12 g / l
• ash at 900 ° C: 2.8 g / l.

A first cationic starch was used, namely that of Example 1, which was prepared by cooking in a continuous cooker.

A second cationic starch, namely a cationic starch having an average DS of 0.12 (1% nitrogen fixed) referenced AMIDON 608, was also used.

The anionic starch used is one of those used in Example 1, namely the sulfosuccinate of VECTOR® A 180 starch.

STARCH 608 and VECTOR® A 180 were cooked in open vats with live steam (5 minutes at 95-98%) from a milk with 4% commercial dry matter. The glues thus obtained were then diluted to 2% with cold water.

The installation used is that shown in the single figure.

• mélangeur M₁ : agitation de 1000 tours/minute,
• mélangeur M₂ : agitation de 2000 tours/minute,
• les débits des pompes P₁ et P₂ : 500 millilitres par minute ; le débit de la pompe P₃ : 400 millilitres par minute ; l'excédent est éliminé.

The operating parameters of this installation have been defined as follows:

• mixer M ₁ : stirring at 1000 revolutions / minute,
• mixer M ₂ : stirring at 2000 rpm,
• the flow rates of pumps P ₁ and P ₂ : 500 milliliters per minute; the flow rate of the pump P ₃ : 400 milliliters per minute; the excess is eliminated.

The cationic starches were introduced by element 8, which gives a contact time of 5 minutes.

The anionic starch was introduced by element 12, which gives a contact time of 30 seconds.

As already indicated above, the amounts of anionic starch used are those for which the turbidimetric reading is the lowest.

ESSAI 12 : néant (essai témoin)

ESSAI 13 : 1,5% de AMIDON 608

ESSAI 14 : 1,5% de HI-CAT® 180

ESSAI 15 : 2 % de AMIDON 608

ESSAI 16 : 2 % de AMIDON 608+0,96% de VECTOR® A 180.

Five tests were carried out (12 to 16), the amounts of starch introduced being:

TEST 12: none (control test)

TEST 13: 1.5% of AMIDON 608

TEST 14: 1.5% of HI-CAT® 180

TEST 15: 2% of AMIDON 608

TEST 16: 2% of AMIDON 608 + 0.96% of VECTOR® A 180.

The turbidity measurements and the fabric retention measurements were carried out and evaluated using the photometer. the overall proportion of starch fixed in canvas water.

The results are collated in Table V. Test Turbidity (water under canvas)% Photometer reading (Starch) "Canvas retention" 12 42 2.215 81 13 37.5 1.675 84.3 14 44 2,660 81.5 15 36.5 2.09 84.5 16 32 1.675 87.4 The pH of the canvas water is 6.2 to 6.4.

Tests 13, 14 and 15 (cationic starch only) clearly demonstrate that, under the conditions retained for this example, the use of a cationic starch of higher DS makes it possible to increase the retention while bringing a lightening of the waters under canvas.

Test 16 shows that the successive use of a cationic starch of the AMIDON 608 type and a anionic starch leads to very clear water under canvas despite high doses of starchy 3%) and excellent retention. In addition, the amount of starch attached is remarkable.

EXAMPLE 4

In the context of this example, a different type of fibrous composition was used than those envisaged so far; it is a paste called "acid medium" but charged, in this case with kaolin.

The composition was taken from an industrial machine, then diluted with the canvas water from from the same machine.

• concentration totale :   11 g/l
• concentration en matières solubles :   0,86 g/l
• pH :   5,6
• acidité en H₂S0₄ :   20 mg/l
• résistivité :   1917 Ω-cm
• sucres réducteurs :   0 g/l
• amidon soluble :   0,31 g/l
• aluminium soluble :   1 mg/l
• cendres à 900°C :   1.6 g/l.

Analysis of the preparation thus obtained gave the following elements:

• total concentration: 11 g / l
• soluble matter concentration: 0.86 g / l
• pH: 5.6
• acidity in H ₂ S0 ₄ : 20 mg / l
• resistivity: 1917 Ω-cm
• reducing sugars: 0 g / l
• soluble starch: 0.31 g / l
• soluble aluminum: 1 mg / l
• ash at 900 ° C: 1.6 g / l.

A cationic starch with a fixed nitrogen level was used as the cationic starch on dry between 0.35 and 0.40 (i.e. a DS between 0.04 and 0.046), in this case that marketed by the Applicant Company under the HI-CAT® 142 brand.

The mode of preparation specific to its implementation is that described for the cationic starch HI-CAT® 180.

In addition, anionic starch VECTOR® A 180 has already been used as anionic starch. described in Example 1.

We always use the installation shown in the single figure.

• mélangeur M₁ : agitation de 1000 tours/minute,
• mélangeur M₂ : agitation de 2000 tours/minute,
• débits des pompes P₁, P₂ et P₃ : 400 ml/minute.

The operating parameters of the installation are defined as follows:

• mixer M ₁ : stirring at 1000 revolutions / minute,
• mixer M ₂ : stirring at 2000 rpm,
• flow rates of pumps P ₁ , P ₂ and P ₃ : 400 ml / minute.

The cationic starch is introduced through element 8, which gives a contact time of 5 minutes.

The anionic starch is introduced through element 12, which gives a contact time of 30 seconds.

ESSAI 17 : Témoin (néant)

ESSAI 18 : 1,2% de HI-CAT® 142

ESSAI 19 : 1,2% de HI-CAT® 142 - 0,66% de VECTOR® A 180.

Three tests are carried out (17 to 19), the amounts of cationic and anionic starch introduced being:

TEST 17: Witness (none)

TEST 18: 1.2% HI-CAT® 142

TEST 19: 1.2% of HI-CAT® 142 - 0.66% of VECTOR® A 180.

The turbidity, the web retention, the load retention were measured and the proportion of starch fixed by photometry.

The results are collated in Table VI. Test Turbidity "Canvas retention"% Load retention% Photometer reading (starch) 17 79 86.9 77.3 2.46 18 72 88.1 78.4 2.66 19 35.5 94.5 90.6 2.57

It follows from this table that the sequential use of anionic starch and cationic starch allows, from the point of view of retention, to obtain remarkable results while impoverishing considerably the waters under canvas.

The fixing of the starches on the fibers is likewise improved.

EXAMPLE 5

Another series of tests was carried out using an unfilled paper pulp, worked in a medium neutral.

• 40% de Kraft blanchi
• 15% de pâte mécanique blanchie - fibres longues
• 45% de pâte mécanique blanchie - fibres courtes.

The basic composition is here:

• 40% bleached Kraft
• 15% bleached mechanical pulp - long fibers
• 45% bleached mechanical pulp - short fibers.

By diluting the thick industrial paste with water under canvas from a machine, the preparation is obtained using which the installation is fed according to the single figure.

• concentration totale :   12,5 g/l
• concentration en matières solubles :   1 g/l
• pH :   5,8
• acidité en H₂S0₄ :   21 mg/l
• résistivité :   1542 Ω-cm
• sucres réducteurs :   0,17 g/l
• amidon soluble :   0,38 g/l
• aluminium soluble :   0,6 mg/l
• cendres à 900°C :   3,3 g/l.

The analysis of this preparation gives the following values:

• total concentration: 12.5 g / l
• soluble matter concentration: 1 g / l
• pH: 5.8
• acidity in H ₂ S0 ₄ : 21 mg / l
• resistivity: 1542 Ω-cm
• reducing sugars: 0.17 g / l
• soluble starch: 0.38 g / l
• soluble aluminum: 0.6 mg / l
• ash at 900 ° C: 3.3 g / l.

Using the installation according to the single figure, the known one was used as cationic starch under the brand HI-CAT® 142 and, as anionic starch, that known under the brand VECTOR® A 180.

• mélangeur M₁ : agitation de 1000 tours/minute,
• mélangeur M₂ : agitation de 2000 tours/minute,
• débits des pompes P₁, P₂ et P₃ : 400 mllminute.

The operating parameters of the installation are as follows:

• mixer M ₁ : stirring at 1000 revolutions / minute,
• mixer M ₂ : stirring at 2000 rpm,
• flow rates of pumps P ₁ , P ₂ and P ₃ : 400 mllminute.

The pH is adjusted to a value of 7-7.2 by introduction of diluted sodium hydroxide at the junction 20 of the pipeline 19 and 9.

Furthermore, the cationic starch is introduced through element 8, which gives a contact time of 5 minutes.

The anionic starch is introduced through element 12, which gives a contact time of 30 seconds.

ESSAI 20 : Témoin (néant)

ESSAI 21 : 1,2% de HI-CAT® 142 et

ESSAI 22 : 1,2% de HI-CAT® 142 et 0,54% de VECTOR® A 180.

Three tests were carried out (20 to 22), the nature and the quantities of starch introduced being:

TEST 20: Witness (none)

TEST 21: 1.2% of HI-CAT® 142 and

TEST 22: 1.2% of HI-CAT® 142 and 0.54% of VECTOR® A 180.

The amount of anionic starch was chosen so that the most turbidimetric reading is obtained low.

• du grammage (en g/m²)
• du Scott-Bond (en Joules/m², norme TAPPI T 506 su 68)
• des cendres (en %)

ont conduit aux résultats réunis dans le tableau VII. Essai Grammage (en g/m²) Scott-Bond (en Joules/m²) Cendres (en %) 20 105 168 15,9 21 115 239 17,8 22 118 330 19,2 The physical tests carried out on the papers obtained from tests 20 to 22, namely the determination:

• grammage (in g / m ² )
• Scott-Bond (in Joules / m ² , TAPPI T 506 su 68 standard)
• ash (in%)

led to the results collated in table VII. Test Grammage (in g / m ² ) Scott-Bond (in Joules / m ² ) Ash (in%) 20 105 168 15.9 21 115 239 17.8 22 118 330 19.2

The values collected in Table VII show that the results obtained are remarkable.

Following what and whatever the embodiment adopted, there is thus a manufacturing process paper whose characteristics result from the above and which has the advantage of leading to results clearly superior to those obtained by implementing the methods according to the prior art.

Claims (8)

1. Process for manufacturing paper, in an installation comprising a wet part, from a starting material constituted by a fibrous composition comprising pastes stemming from salvaged cellulose fibres or recycled pastes, wherein are introduced into said fibrous composition, in two or several points of the installation located in particular in the wet part thereof, separately from one another, from 0.2 to 5% of one or several cationic starches and from 0.2 to 5% of one or several anionic starches chosen in the group constituted by starch sulfates, starch sulfocarboxyls and starch carboxyalkyls, these percentages being expressed as dry starch with respect to the dry fibrous composition, the proportion of cationic starch with respect to the anionic starch being comprised between 10/1 and 1/10, these ratios being expressed as dry weight of starch.
2. Process for manufacturing paper according to claim 1, characterized by the fact that the cationic starches are selected from among those having an acceptor electron state, obtained by means of substituent groups of an electropositive nature, the substituents most currently used being those containing a tertiary or quaternary nitrogen atom, phosphonium and sulfonium groups also being useable.
3. Process according to claim 2, characterized by the fact that the degree of substitution of the cationic starch employed is at the most equal to 0.3, preferably comprised between 0.02 and 0.20 and, more preferably, between 0.04 and 0.15.
4. Process for manufacturing paper according to one of ciaims 1 to 3, characterized by the fact that the anionic starch is selected from the group comprising carboxymethyl starches, succinyl starches, starch sulfosuccinates, sulfated starches.
5. Process according to claim 4, characterized by the fact that the degree of substitution of the anionic starch employed is at the most equal to 1.5, preferably at the most equal to 0.5.
6. Process for manufacturing paper according to one of claims 1 to 5, characterized by the fact that the amounts of cationic and anionic starch employed are comprised between 0.4 and 3%, more preferably between 0.7% and 2.5%, the percentages being expressed as dry starch with respect to the dry fibrous composition.
7. Process for manufacturing paper according to one of claims 1 to 6, characterized by the fact that the cationic and anionic starches are introduced into the fibrous composition in the form of a dilute aqueous glue of concentration less than 5%, preferably less than 3% and, more preferably, less than 1%, the lower limit being 0.01%.
8. Process for manufacturing paper according to one of claims 1 to 7, characterized by the fact that the proportion of cationic starch with respect to the anionic starch is comprised between 5/1 and 1/3 and, preferably, between 3/1 and 1/2, these ratios being expressed as dry weight of starch.

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