EP1138824A1 - Additive composition for the paper industry, and process for using the same - Google Patents

Abstract

A formulation used in the fabrication of paper or cartons used in humid conditions comprises a clay (45 wt.%), a binder (45 wt.%) and a retention agent (10 wt.%) all in powder form. An INDEPENDENT claim is included for a fabrication process for the paper/carton starting with recycled paper fibres comprising: (i) formation of a thick cake from the fibres; (ii) refining the cake; (iii) formation of a diluted cake; (iv) mixing into the diluted cake additives especially cured starch and a retention agent; (v) formation of a layer; and (vi) drying of the layer.

Description

The present invention relates to a formulation additives for the paper industry and a process for implementation of such a formulation.

The area concerned is more particularly that wet paper and cardboard manufacturing, including in particular a dehydration stage (by draining, drying, etc.) and shaping on canvas, from recycled cellulosic fibers.

• un agent de rétention, notamment un polymère, de préférence à haut poids moléculaire, par exemple un polyacrylamide, qui est connu pour améliorer la floculation dans la pâte à papier ; et
• un agent liant, par exemple de l'amidon, la gomme guar ou l'acide silicique, qui améliore la cohésion interne de la pâte en s'associant avec les fibres cellulosiques, améliorant de ce fait les caractéristique physiques (par exemple la solidité) du papier ou du carton final.

The following main additives are conventionally used to improve the characteristics of the paper or cardboard obtained and the yield of the formation process:

• a retention agent, in particular a polymer, preferably of high molecular weight, for example a polyacrylamide, which is known to improve flocculation in paper pulp; and
• a binding agent, for example starch, guar gum or silicic acid, which improves the internal cohesion of the pulp by associating with the cellulose fibers, thereby improving the physical characteristics (for example the solidity) final paper or cardboard.

• un matériau minéral, comme de l'argile, par exemple de la bentonite, qui, grâce à sa surface spécifique très développée, est utilisé pour sa capacité d'absorption ;
• une charge minérale, comme les carbonates kaolin, destinée à remplacer les fibres cellulosiques qui sont coûteuses en remplissant et colmatant les interstices entre les fibres ;
• un ou plusieurs agents cationiques pour neutraliser les sites anioniques des fibres cellulosiques et permettre de mieux maítriser le comportement de la pâte à papier ; ces agents pouvant être notamment un polyélectrolyte cationique, le polymère floculant de nature cationique, un coagulant, l'amidon, un agent de rétention, un agent d'égouttage ; ou encore
• des colorants ; antimousses ; etc.

We also recommend the use of the following additives depending on the type of paper or cardboard we are looking for:

• a mineral material, such as clay, for example bentonite, which, thanks to its highly developed specific surface, is used for its absorption capacity;
• a mineral filler, such as kaolin carbonates, intended to replace the cellulosic fibers which are expensive by filling and plugging the interstices between the fibers;
• one or more cationic agents to neutralize the anionic sites of cellulose fibers and allow better control of the behavior of the pulp; these agents possibly being in particular a cationic polyelectrolyte, the flocculating polymer of cationic nature, a coagulant, starch, a retention agent, a draining agent; or
• dyes; defoamers; etc.

• un pulpeur 1 dans lequel on introduit des fibres cellulosiques et de l'eau ;
• des moyens de raffinage 2 (non détaillés ici) qui dégrossissent la pâte à papier formée dans le pulpeur 1, en éliminant notamment les grosses particules ;
• un cuvier permettant la dilution de la pâte avant son arrivée sur la toile de formation de la machine à papier ;
• une pompe de mélange 4 qui permet de réaliser un mélange homogène avec des adjuvants introduits en amont de la pompe 4 ;
• une pompe sous pression 5 qui permet de réaliser un mélange homogène de la pâte avec des adjuvants et de l'envoyer sous pression vers la machine à papier ;
• un dispositif 6 de formation d'une feuille de papier comprenant une caisse de tête 7, une toile de formation 8 d'une feuille de papier et un récupérateur 9 des eaux usées (appelées couramment «eaux blanches»);
• une sécherie 10 ; et
• des moyens de recyclage 11 des eaux blanches vers le pulpeur 1.

In FIG. 1, the traditional manufacturing circuit comprising:

• a pulper 1 into which cellulosic fibers and water are introduced;
• refining means 2 (not detailed here) which rough the paper pulp formed in the pulper 1, in particular by removing large particles;
• a vat allowing the dilution of the pulp before its arrival on the fabric of formation of the paper machine;
• a mixing pump 4 which makes it possible to produce a homogeneous mixture with adjuvants introduced upstream of the pump 4;
• a pressure pump 5 which makes it possible to produce a homogeneous mixture of the pulp with adjuvants and to send it under pressure to the paper machine;
• a device 6 for forming a sheet of paper comprising a head box 7, a fabric 8 for forming a sheet of paper and a collector 9 for waste water (commonly called "white water");
• a dryer 10; and
• recycling means 11 from the white water to the pulper 1.

At the outlet of the refiners 2 there is a thick paste. AT the outlet of device 3 from the dilution vat until head box 7, we have a diluted paste and then a sheet of cardboard or paper.

• de l'amidon cuit en amont de la pompe de mélange 4 ; et
• l'agent de rétention en aval de la pompe 4 et en amont de la pompe sous pression 5.

The main additives are conventionally introduced into this circuit as follows:

• starch cooked upstream of the mixing pump 4; and
• the retention agent downstream of the pump 4 and upstream of the pressure pump 5.

To strengthen the final characteristics of the leaf it is also known to spray starch native (uncooked) on formation cloth 8, starch which is then cooked in the dryer 10.

In international patent application WO98 / 22653, another process is described (shown diagrammatically in the figure 2 with the same references as in FIG. 1), having intended to introduce a large amount of starch into the final sheet. The method consists in introducing into the diluted paste upstream of the mixing pump 4, a suspension containing mainly particles not dissolved starch to which a retention agent is added consisting of a cationic flocculating polymer and an agent said to "help the agglomeration" consisting of a network anionic microparticulate, such as bentonite. Of the retention agent is then conventionally introduced upstream of the pressure pump 5 and it is recommended to introduce bentonite also into the body of head 7. Preferred proportions as a percentage by weight based on the total weight of the starch mixture> 93%, agglomeration aid> 4% and polymer> 3%. The authors describe that the flocculating polymer and helps it the agglomeration interact to provide a network of flocculation in which the starch particles are trapped. This process would improve retention starch in the formed sheet of paper.

The synergistic effect of the bentonite and polymer system at high molecular is also known, bentonite promoting "micro-flocculation" of solids, helping thus to the uniformity of cardboard or paper formation and to the acceleration of the drainage on the canvas of the machine.

The object of the present invention is to improve the process for manufacturing paper or cardboard by wet, specifically from fibers from old paper. With this type of raw material, a cellulosic suspension is formed in the pulper containing soluble or partially soluble matter and colloidal, including "old starch". The current invention aims to treat these materials so as to reduce the content in white water discharged into effluents to reduce chemical demand by oxygen.

• une présentation sous forme de poudre ; et
• les proportions suivantes en % en poids par rapport au poids de la formulation :
  • argile : sensiblement 45 %
  • liant : sensiblement 45 %
  • agent de rétention : sensiblement 10 %.

It proposes a formulation of adjuvants comprising a clay, a binder and retention agent characterized by:

• a presentation in powder form; and
• the following proportions in% by weight relative to the weight of the formulation:
  • clay: approximately 45%
  • binder: substantially 45%
  • retention agent: substantially 10%.

• formation d'une pâte épaisse à partir desdites fibres ;
• de raffinage de ladite pâte ;
• de formation d'une pâte diluée ;
• d'introduction et de mélange d'adjuvants à la pâte diluée, notamment de l'amidon cuit et de l'agent de rétention ;
• de formation d'une feuille ; et
• de séchage de ladite feuille ;

ledit procédé étant caractérisé en ce que l'on ajoute la formulation selon l'invention dans ladite pâte épaisse, en amont ou en aval de l'étape de raffinage.It also offers a process for the manufacture of paper or cardboard by the wet method from fibers originating from recycled paper, comprising the essential steps of:

• forming a thick paste from said fibers;
• refining said dough;
• forming a diluted paste;
• introducing and mixing adjuvants to the diluted dough, in particular cooked starch and the retention agent;
• forming a sheet; and
• drying said sheet;

said process being characterized in that the formulation according to the invention is added to said thick paste, upstream or downstream of the refining step.

This process is shown schematically in Figure 3 with the use of the same references as for FIGS. 1 and 2.

The originality of the present invention therefore consists to bring together three adjuvants which were traditionally introduced separately to different stages of the paper or cardboard manufacturing process in a single product, in powder form, which is introduced very early in the manufacturing circuit, when of the thick dough preparation step.

• le but recherché est différent : selon l'invention on cherche à capturer l'amidon contenu dans la suspension cellulosique pour l'incorporer dans la feuille finale ; selon WO 98/22653 on cherche à introduire le maximum d'amidon dans la feuille finale à partir d'amidon rajouté ;
• le stade d'introduction est différent : selon l'invention, l'introduction se fait très tôt dans le circuit à savoir dans la pâte épaisse alors que selon WO 98/22653 l'introduction se fait plus tard dans la pâte diluée ;
• l'état physique de la formulation est différent selon l'invention, la formulation se présente sous forme d'une poudre alors que selon WO 98/22653 la formulation est introduite sous forme de boue coagulée ou suspension liquide ; et
• les proportions des constituants sont très différentes, notamment la quantité d'amidon dans la formulation de WO 98/22653 est beaucoup plus importante que selon l'invention.

The method according to the invention differs from the method described in document WO 98/22653 essentially by the fact that:

• the aim sought is different: according to the invention, it is sought to capture the starch contained in the cellulose suspension in order to incorporate it into the final sheet; according to WO 98/22653 it is sought to introduce the maximum of starch into the final sheet from added starch;
• the introduction stage is different: according to the invention, the introduction takes place very early in the circuit, namely in the thick paste while according to WO 98/22653 the introduction takes place later in the diluted paste;
• the physical state of the formulation is different according to the invention, the formulation is in the form of a powder whereas according to WO 98/22653 the formulation is introduced in the form of coagulated mud or liquid suspension; and
• the proportions of the constituents are very different, in particular the amount of starch in the formulation of WO 98/22653 is much greater than according to the invention.

Surprisingly and as will emerge from comparative examples given below, we were able to observe a decrease in the content of rejected adjuvants in effluents with better retention of these in the formed sheet, and therefore reduce substantially the necessary amount of adjuvants, including the binder and the retention agent, which are traditionally introduced later in the manufacturing circuit.

There has also been a marked improvement in physical characteristics of the finished product.

The content of each of the formulation adjuvants according to the invention can be adjusted according to the desired application, namely the type of fibers recycled used, characteristics expected for the final product etc.

In the formulation according to the invention, the clay serves to capture the soluble elements provided by the material first recycling as well as introducing many sites capable of reacting electrostatically with other sites in the total composition of the dough.

Preferably, bentonite is chosen comprising the family of lamellar silicates which swells in presence of water, either naturally or after activation by treatment for example with carbonate sodium. These may in particular be montmorillonites, seppiolites, attapulgites, saponites or holloysites.

Preferably, one chooses for the formulation a binder poorly soluble in water thus also serving as mineral filler to obtain a microparticulate structure. Preferably choose native starch which will be "cooked" during the drying stage of the process.

The fixing agent will preferably be a polymer cationic having a molecular weight between 50,000 and 3,500,000, preferably between 1,000,000 and 2,000,000. A polyacrylamide is preferably chosen. He has for function of fixing clay and starch on the surface of cellulosic fibers.

• pour l'argile : une granulométrie > 100 microns, de préférence encore entre 25 et 50 microns ;
• pour le liant : une granulométrie > 150 microns, de préférence encore entre 10 et 100 microns ; et

From a particle size point of view, we will prefer:

• for clay: a particle size> 100 microns, more preferably between 25 and 50 microns;
• for the binder: a particle size> 150 microns, more preferably between 10 and 100 microns; and

The Claimants believe that the mechanism reaction is as follows. The presence of water in the dough would start the development of the surface of clay by swelling of its particles and structure spongy would absorb and trap colloids. By the same action, the binder would also be picked up, less partially, by clay. For his part, the agent fixer would dissolve over time to first coagulate fine suspended particles. Then, the extension of the molecular chains would link the clay and the remaining binder on the cellulosic fibers by reaction with hydroxyl groups. The presence of binder inside the clay structure and on the surface of cellulosic fibers remains acquired in the sheet of paper or cardboard finished. Indeed, after the formation of the sheet for example on a canvas, this binder enters the drying stage where it cooks and bursts under the effect of the rapid rise in temperature, for increase the internal bonds of the sheet of paper or cardboard.

• de diminuer la demande ionique et donc la quantité de polymère de rétention ;
• d'assainir les effluents grâce à la capture des polluants colloïdaux apportés par la matière de recyclage vers les fibres cellulosiques solides ;
• d'introduire des particules minérales qui servent ensuite de base de réaction dans des traitements subséquents ;
• d'introduire un agent liant (l'amidon) sur la surface des fibres cellulosiques et à l'intérieur de la feuille de papier ou de carton.

Such a method makes it possible in particular:

• to reduce the ionic demand and therefore the quantity of retention polymer;
• to clean up the effluents by capturing the colloidal pollutants brought by the recycling material to the solid cellulosic fibers;
• to introduce mineral particles which then serve as a reaction base in subsequent treatments;
• introduce a binding agent (starch) on the surface of the cellulose fibers and inside the sheet of paper or cardboard.

The dosage can vary from 0.5 to 5 kg / tonne (in relation solid / solid) but is in practice between 2 and 3 kg / ton.

• la figure 1 illustre schématiquement le circuit de fabrication selon l'art antérieur ;
• la figure 2 est une vue similaire à la figure 1 montrant le procédé décrit dans la demande internationale WO 98/22653 ;
• la figure 3 est une vue similaires aux figures 1 et 2 illustrant le procédé selon l'invention ;
• la figure 4 donne le tableau 1 de résultats de l'exemple comparatif n°1 ; et
• la figure 5 le tableau 2 de résultats de l'exemple comparatif n°2.

The present invention will be better understood and other advantages will appear in the light of the description which follows of embodiments, description made with reference to the appended drawings in which:

• Figure 1 schematically illustrates the manufacturing circuit according to the prior art;
• Figure 2 is a view similar to Figure 1 showing the process described in international application WO 98/22653;
• Figure 3 is a view similar to Figures 1 and 2 illustrating the method according to the invention;
• FIG. 4 gives the table 1 of results of comparative example n ° 1; and
• Figure 5 Table 2 of results of Comparative Example 2.

Comparative example n ° 1 (see figure 3 table 1)

Three tests were carried out on a cardboard machine Fourdrinier type (flat table). We were looking for a very heavy quality of cardboard sheet, 440 gsm, manufactured in a single layer, so-called "cover" quality.

The pulp used contained 100% recycled paper.

Ambient temperature in the laboratory for testing control was 25 ° C and the humidity 50%.

For each test, the classic resistance tests (bursting, tearing, crushing, delamination and break length) were made to characterize the sheet of cardboard obtained.

For each test, the D.C.O. was also measured. waters under canvas.

Test No. 1: a mixture of two binders was used, comprising: 18.70 kg / t of native starch and 1.74 kg / t of guar gum from China. This mixture was also introduced into the thick paste. Nine series of measurements were carried out and the results are reported in Table 1.

Test No. 2: the same mixture of binders was used but with a larger tonnage: 19.91 kg / t of native starch and 1.83 kg / t of guar gum. Was this mixture also introduced in step? ? ? Nine series of measurements were carried out and the results are reported in Table 1.

Test No. 3: A formulation according to the invention consisting of a powder containing 45% by weight of native starch, 45% by weight of bentonite and 10% by weight of polyacrylamide, was added upstream of the refining stages of thick dough. The quantity introduced was 2 kg / t. The particle size in this example was much less than 100 microns. The same mixture of binders was introduced at the same stage of the process. Seven series of measurements were carried out and the results are reported in Table 1.

Observations:

Between trial 1 and trial 2, the increase in the amount of binders did not increase the physical properties of the cardboard sheet but only to increase the D.C.O. waters under canvas which goes from 6890 mg / l to 7240 mg / l.

• de diminuer la D.C.O. de 6890 mg/l à 4780 mg/l ;
• de diminuer la quantité d'amidon natif de 18,70 kg/t à 15,53 kg/t et la quantité de gomme guar de 1,83 kg/t à 1,52 kg/t ;
• d'améliorer les caractéristiques physiques de la feuille de carton obtenue (voir les valeurs dans le tableau 1).

On the other hand, the addition of the formulation according to the invention significantly enabled:

• reduce the COD from 6890 mg / l to 4780 mg / l;
• reduce the amount of native starch from 18.70 kg / t to 15.53 kg / t and the amount of guar gum from 1.83 kg / t to 1.52 kg / t;
• to improve the physical characteristics of the cardboard sheet obtained (see the values in table 1).

The reduction in the quantity of the two binders allows advantageously increase the production yield of the machine.

Comparative example n ° 2 (see figure 4 table 2)

Three tests were carried out on a cardboard machine Fourdrinier type (flat table). We were looking for a quality of cardboard sheet (140 gsm), made in two layers glued together before being dried. The quality of the cardboard sheet sought was test white liner (???).).

• couche inférieure : papiers recyclés mélangés : 57%
• couche supérieure : papiers recyclés blancs : 43%.

The pulp used contained 100% recycled paper:

• bottom layer: mixed recycled paper: 57%
• upper layer: white recycled paper: 43%.

Ambient temperature in the laboratory for testing control was 25 ° C and the humidity 50%.

For each test, the resistance tests to the bursting and the crushing were carried out for characterize the cardboard sheet obtained. Five sets of measurements have been taken and the results are reported in table 2.

Test No. 1: Cooked starch is introduced into the dough vat diluted in cationic form at 3% relative to the weight of the dough. Native starch, that is to say "uncooked" starch, is sprayed on each layer at a rate of 1% relative to the weight of each sheet.

Test No. 2: The procedure was as in Test No. 1 and, in addition, during the manufacture of the upper layer, a formulation according to the invention was added, consisting of a powder containing 45% by weight of native starch, 45 % by weight of bentonite and 10% by weight of polyacrylamide, downstream of the refining stages of the thick paste. The amount introduced was 0.10% relative to the dry weight of the dough. The particle size in this example was much less than 100 microns.

Test No. 3: Cooked starch is introduced into the dough vat diluted in cationic form to only 2% relative to the weight of the dough and the same formulation was added according to the invention as in test No. 2 but with a higher percentage (0.20%).

Observations:

Between test n ° 1 and test n ° 2, the addition of the formulation according to the invention made it possible to increase significantly the physical properties of the sheet of cardboard (see the values given in table 2).

• supprimer complètement l'amidon sous forme pulvérisée ;
• augmenter de manière très significative les caractéristiques physiques du carton obtenu, notamment la résistance à l'éclatement ; et
• diminuer la quantité d'amidon cationique de 3% à 2%.

Test No. 3 shows that it is possible, thanks to the formulation according to the invention:

• completely remove starch in spray form;
• significantly increase the physical characteristics of the cardboard obtained, in particular the burst strength; and
• decrease the amount of cationic starch from 3% to 2%.

Furthermore, delamination measured with waxes Dennison of progressive bonding degrees between 10 and 20 (by removing one layer of the other with wax) a reaches values much higher than what was observed before and we were able to improve the speed of manufacturing which passed more or less 175 meters per minute over 206 meters per minute (180%)

Claims (9)

Formulation of adjuvants for a process for the manufacture of paper or cardboard by the wet method, comprising a clay, a binder and a retention agent characterized by : a presentation in powder form; and the following proportions in% by weight relative to the weight of the formulation: clay: approximately 45% binder: substantially 45% retention agent: substantially 10%. Formulation according to claim 1, characterized by bentonite as clay. Formulation according to claim 1 or 2, characterized in that the binder is sparingly soluble in water. Formulation according to any one of Claims 1 to 3, characterized in that the binder is an uncooked starch. Formulation according to any one of Claims 1 to 4, characterized in that the retention agent is a cationic polymer. Formulation according to Claim 5, characterized in that the cationic polymer is a polyacrylamide. Formulation according to any one of the preceding claims, characterized in that the cationic polymer has a molecular weight of between 50,000 and 3,500,000. Formulation according to Claim 7, characterized in that the cationic polymer preferably has a molecular weight between 1 000 000 and 2 000 000. Process a process for the manufacture of paper or cardboard by the wet method from fibers originating from recycled papers, comprising the essential steps of: forming a thick paste from said fibers; refining said dough; forming a diluted paste; introducing and mixing adjuvants to the diluted dough, in particular cooked starch and the retention agent; forming a sheet; and drying said sheet; said process being characterized in that the formulation according to any one of claims 1 to 8 is added to said thick paste, upstream or downstream of the refining step.

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