EP0522940B1 - Process for the preparation of paper and paper obtained therefrom - Google Patents

Abstract

Process for the manufacture of paper, characterised in that the following are added to the fibrous composition entering the flow box: a) an inorganic filler, b) an adhesion promoter, and c) a retaining system consisting of: c)1) cationic starch, c)2) aluminium polychloride, and c)3) silica of anionic nature. The products c)1), c)2) and c)3) have the following respective weight percentages on a weight basis in relation to the weight of the composition entering the flow box: 0.15 to 1.7 %, 0.05 to 0.25 % expressed as percentage of Al2O3, and 0.01 to 0.3 % expressed as percentage of SiO2. The cationic starch has a molecular weight of 3x10<4> to 12x10<4> and a degree of substitution of 0.01 to 0.1.

Description

The present invention relates to a process for manufacturing paper and also relates to the paper thus obtained.

The raw paper pulp consisting essentially of cellulose fibers is put into the form of a dilute aqueous suspension which is brought into the headbox of the paper machine from where it is distributed on a filter cloth on which the sheet is formed. of paper. This sheet is then wrung and dried. The qualities and properties of the paper obtained are determined in particular by the operating conditions of the paper machine, the raw pulp, the various additives that are added to the suspension before the sheet is formed and also the products that are coated. on the sheet of paper downstream of the filter cloth.

Among the products added to the suspension of fibers entering the headbox, there may be mentioned mineral fillers, bonding agents, agents intended to improve the mechanical properties of the paper, dyes, etc. Mineral fillers, such as CaCO ₃ , TiO ₂ , etc., make the sheet of paper opaque, which facilitates writing and printing. Sizing agents, such as those of the dimeric alkyl ketene family, are added to make the sheet resistant to liquids, therefore allowing the glued sheet of paper to be used for writing and printing.

One of the qualities of paper, cardboard and others is the regularity of the characteristics. Among these, "the air" or "leaf formation" is of great importance and is representative of the general quality of the paper. In fact, the epair represents the greater or lesser homogeneity of the distribution of the fibers in the plane and the thickness of the sheet. The quality of the air will therefore have a considerable impact on the general quality of printing in the case, for example, of print-writing papers, and on the mechanical properties in the case, for example, of packaging papers. To improve the look, more and more additives are added to the suspension entering the headbox. But to meet the increasingly stringent requirements of pollution standards, paper mills are led to reduce their water consumption, which causes an increase in the pollutant load associated with this type of industry (MES suspended matter, Biological Demand in Oxygen BOD, Chemical Demand in Oxygen COD, Salinity, etc ...) as well as other problems, such as pitch problems and more generally those related to the presence of anionic waste (called in English "anionic trash") . The characteristics of the paper having however to remain identical, and the problems of fight for the environment having to be solved, one of the methods proposed in the prior art consists in increasing the retention of the elements within the sheet being formed on the filter cloth. This result is achieved, to a certain extent, by the addition of retention agents to the suspension of fibers entering the headbox. Unfortunately, this method either varies in efficiency or leads to a significant deterioration in the appearance of the paper depending on the products used.

• EP-A-348 366 décrit un système ternaire comprenant de l'amidon cationique, du polychlorure d'aluminium, et un polymère d'acide silicique. L'acide polysilicique doit avoir une aire spécifique donnée (> 1 050 m²/g).
• WO-A- 88/6 659 décrit un système ternaire comprenant un polymère cationique, du polychlorure d'aluminium, et de la silice. Le polymère cationique est de préférence du polyacrylamide et l'amidon cationique n'est pas cité.
• EP-A-285 486 décrit un système rétenteur à base d'amidon cationique et de polychlorure d'aluminium. La charge minérale peut être par exemple de la silice. Néanmoins, cette demande ne décrit pas spécialement le système rétenteur ternaire selon la présence invention.
• US-A-4 643 801 décrit un système rétenteur à base d'amidon cationique, d'un polymère anionique à poids moléculaire élevé et de silice selon des rations en poids amidon/silice de 100/1 à 1/1 et polymère anionique/silice de 20/1 à 1/10. Un composé d'aluminium peut aussi être ajouté. Le présent système rétenteur ternaire seul n'est cependant pas décrit. WO-A-86/00100 décrit des additifs aux charges de caisses de tête, comprenant un composant type amidon cationique et un composant type silice à surface modifiée. Cette silice modifiée est obtenue par traitement de sa surface avec des ions aluminates, qui subissent un échange. Cette solution technique qui est exclue de l'objet de la revendication 1, est cependant complexe et d'un coût relativement élevé.

The present invention therefore relates to a new process for manufacturing papers and the like, in which, in addition to the mineral filler and the bonding agent is mixed with the suspension or composition of fibers entering the headbox, a new ternary retention system. The state of the art in this area is essentially made up of the following documents:

• EP-A-348 366 describes a ternary system comprising cationic starch, poly aluminum chloride, and a polymer of silicic acid. The polysilicic acid must have a given specific area (> 1050 m ² / g).
• WO-A- 88/6659 describes a ternary system comprising a cationic polymer, poly aluminum chloride, and silica. The cationic polymer is preferably polyacrylamide and the cationic starch is not mentioned.
• EP-A-285 486 describes a retention system based on cationic starch and poly aluminum chloride. The mineral filler can for example be silica. However, this application does not specifically describe the ternary retention system according to the invention.
• US-A-4 643 801 describes a retention system based on cationic starch, a high molecular weight anionic polymer and silica according to starch / silica weight rations of 100/1 to 1/1 and anionic polymer / silica from 20/1 to 1/10. An aluminum compound can also be added. The present ternary retention system alone is however not described. WO-A-86/00100 describes additives to headbox fillers, comprising a cationic starch type component and a silica type component with modified surface. This modified silica is obtained by treating its surface with aluminate ions, which undergo an exchange. This technical solution, which is excluded from the subject of claim 1, is however complex and relatively expensive.

In "Polyaluminium hydroxychloride application in neutral pH rosin sizing of paper", BH Wortley and JC Steelhammer, is mentioned a retentive system comprising cationic starch, bentonite and an anionic polymer, but it is not mentioned nor suggested l use of PAC in this particular retention system.

None of the above publications alone or in combination with other references describes or suggests the use of a retention system of the type of that of the present invention or describes or suggests the surprising and unexpected effects obtained thanks to this. new retention system.

The object of the present invention is, among other things, while retaining the quality of the air and the other characteristics of the paper, to obtain high retention rates as well as to allow improved drainage. The present invention makes it possible to achieve a higher charge, in particular in products sensitive to acids, and leads to less polluting releases. Thus, the present invention has for A process for manufacturing paper according to claim 1.

The suspension containing the cellulose fibers can be raw or bleached pulp, bleached chemical pulp of softwoods or hardwoods or annual plants, unbleached chemical pulp of softwoods or hardwoods, mechanical pulps (SGW, TMP, CTMP, ...) unbleached or bleached, de-inked bleached or unbleached pasta, pasta already containing additives, and mixtures thereof.

The cationic starch - mentioned as component c) 1) - used according to the present invention is a mixture of one or more products sold under the generic name of cationic starch. Starch has an average molecular weight of 2.10 ⁴ to 2.10 ⁵ , preferably 3.10 ⁴ to 12.10 ⁴ . Cationic starches have a degree of substitution (DS) of between 0.01 to 0.1. The cationic starches are, for example, those described in Kirk Othmer, 3rd edition, volume 21, page 503. They represent by weight from 0.2 to 1.7% of the weight of the fibrous suspension entering the headbox.

• 1. le sel de formule:
  
          Al_n(OH)_mCl_3n-m     (I)
  
  dans laquelle 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/A1 étant de préférence compris entre 0,015 et 0,4;

• 2. le sel de formule:
  
          Al_n(OH)_mCl_3n-m-2k(SO₄)k     (II)
  
  dans laquelle k, m et n sont des entiers positifs, et 3n > m + 2k, la basicité ou le rapport m/3n est compris entre 0,3 et 0,7 et k/n = 0,01 à 0,03;

ce produit peut être préparé selon le procédé décrit dans le US-A-3 929 666;

• 3. le sel de formule:
  
          [Al_n(OH)_3n-m-2pCl_m(SO₄)_p]z     (III)
  
  dans laquelle (3n-m-2p)/3n = 0,4 à 0,7; p = 0,04 à 0,25n; m/p = 8 à 35; k, m, n, et p sont des nombres entiers et z est au moins 1;

ce produit est décrit dans GB-A-2 128 977;

• 4. le chlorosulfate d'aluminium basique de formule:
  
          Al_nOH_m(SO₄)_kCl_3n-m-2k     (IV)
  
  dans laquelle la basicité ou le rapport molaire (m/3n)x100 est compris entre 40% environ et 65% environ

qui présente un rapport équivalent Al/équivalent Cl compris entre 2,8 et 5, une masse moléculaire apparente MA, mesurée par diffusion de lumière classique, et des diamètres hydrodynamiques apparents ØZ et ØW, mesurés par diffusion quasi-élastique de la lumière, présentant les valeurs respectives suivantes:

• MA = 7000-35000
• ØZ(Å) = 350-2500
• ØW(Å) = 200-1200;

ce produit est décrit dans FR-A-2 584 699.Poly aluminum chloride or "PAC" - mentioned as component c) 2) - used according to the present invention designates the products which are usually called poly aluminum chloride, basic aluminum polychloride, basic aluminum polychlorosulfate, and preferably consists of one or more of the following products:

• 1. the salt of formula:
  
  Al _n (OH) _m Cl _3n-m (I)
  
  where n is arbitrary, 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 / A1 preferably being between 0.015 and 0.4;

• 2. the salt of formula:
  
  Al _n (OH) _m Cl _3n-m-2k (SO ₄ ) k (II)
  
  in which k, m and n are positive integers, and 3n> m + 2k, the basicity or the ratio m / 3n is between 0.3 and 0.7 and k / n = 0.01 to 0.03;

this product can be prepared according to the method described in US-A-3,929,666;

• 3. the salt of formula:
  
  [Al _n (OH) _3n-m-2p Cl _m (SO ₄ ) _p ] z (III)
  
  in which (3n-m-2p) / 3n = 0.4 to 0.7; p = 0.04 to 0.25n; m / p = 8 to 35; k, m, n, and p are whole numbers and z is at least 1;

this product is described in GB-A-2 128 977;

• 4. basic aluminum chlorosulfate of formula:
  
  Al _n OH _m (SO ₄ ) _k Cl _3n-m-2k (IV)
  
  in which the basicity or the molar ratio (m / 3n) x100 is between approximately 40% and approximately 65%

which has an equivalent Al / equivalent Cl ratio between 2.8 and 5, an apparent molecular mass MA, measured by conventional light scattering, and apparent hydrodynamic diameters ØZ and ØW, measured by quasi-elastic scattering of light, having the following respective values:

• MA = 7000-35000
• ØZ (Å) = 350-2500
• ØW (Å) = 200-1200;

this product is described in FR-A-2 584 699.

PAC is present in the fiber composition entering the headbox at a rate of 0.01 to 0.3% by weight, relative to the weight of said fibrous composition, said percentage being expressed relative to Al ₂ O ₃ . Preferably, the PAC is from WAC. The WAC corresponds to formula IV.

The silica is present in the fibrous composition in an amount of 0.01 to 0.3% by weight, relative to the weight of said fibrous composition, the percentage being expressed as a percentage of active material, that is to say in SiO ₂ . The anionic silica used is that which is in the form of a silica sol, advantageously at 15% of SiO ₂ .

The mineral filler - component a) mentioned above - can be one or more of the following conventionally used fillers, given by way of illustration: clay, CaCO ₃ , hydrated alumina, talc, TiO ₂ , etc. The mineral filler represents 5 to 30% by weight, preferably 10 to 25% by weight, of the weight of said fibrous composition. The preferred mineral filler is formed from CaCO ₃ .

The sizing agent - component b) mentioned above - can be one or more of the following agents conventionally used in neutral medium: dimeric alkyl ketenes (AKD), fluorinated phosphates, carboxylic anhydrides, styrene / maleic anhydride copolymers, and their derivatives . The amount of sizing agent used is between 0.01 and 2% by weight of commercial product at 6% of active material, relative to the weight of said composition. The bonding agent preferably used is AKD.

The components a), b), c) 1), c) 2) and c) 3) mentioned above can be added separately or as a mixture of two or more of them.

The fibrous suspension can also contain conventional additives, such as dyes, optical brighteners, mechanical reinforcing agents, defoamers, antislimes (anti-deposition agent), as well as products chosen from the group consisting of: polyacrylamides , polyethyleneimines, carboxymethylcellulose, urea-formaldehyde resins, melamine-formaldehyde resins, aminopolyamide-epichlorohydrin resins, polyamide-epichlorohydrin resins.

• a) de 5 à 30% de CaCO₃,
• b) de 0,01 à 1% d'AKD, et
• c) 1. de 0,2 à 1,7% d'amidon cationique de poids moléculaire 2.10⁴ à 12.10⁵ et de degré de substitution de 0,01 à 0,1; c)2. de 0,1 à 3% de WAC en produit commercial à 10% de Al₂O₃; et c)3. de 0,01 à 0,3% de sol de silice, exprimé en % de SiO₂.

Preferably, the added components are:

• a) from 5 to 30% of CaCO ₃ ,
• b) from 0.01 to 1% of AKD, and
• c) 1. from 0.2 to 1.7% of cationic starch of molecular weight 2.10 ⁴ to 12.10 ⁵ and of degree of substitution from 0.01 to 0.1; c) 2. from 0.1 to 3% of WAC in commercial product to 10% of Al ₂ O ₃ ; and c) 3. from 0.01 to 0.3% silica sol, expressed as% of SiO ₂ .

The following examples are illustrative of the present invention and should in no way be taken to limit it. In these examples, WAC is a product marketed by ATOCHEM and corresponds to a poly aluminum chloride of formula IV at 10% Al ₂ O ₃ . The silica is in the form of a silica sol and is commercially available under the name CECASOL from CECA. The cationic starch is that manufactured by ROQUETTE and marketed under the name HICAT 142. The AKD sizing agent is manufactured by HERCULES and marketed under the name AQUAPEL.

Example 1

• . machine utilisée   table plate équipée d'un former BEL BOND
• . vitesse   590 m/mn
• . laize   3 m
• . grammage   50 g/m²

The paper to be made is carbonless printing-writing paper.

• . machine used flat table equipped with a BEL BOND former
• . speed 590 m / min
• . width 3 m
• . grammage 50 g / m ²

Fibrous composition :

• . Pâte kraft blanchie de résineux (KBR)   45%
• . Pâte kraft blanchie de feuillus (KBF)   55%
• . Charge   CaCO₃
• . Taux de charge du papier fini   14%
• . Collage (AKD)   0,15%
• . Amidon cationique   0,6%

Les essais effectués sur le produit obtenu, dans les conditions consignées dans le Tableau ci dessous, conduisent aux résultats donnés dans ce tableau: RESULTATS WAC Silice (1) Rétention totale Epair (2) Essai 1 ... 0 0,5% 58% 104 Essai 2 ... 1,65% 0 57% 70 Essai 3 ... 1,65% 0,15% 67% 72 (1) En produit commercial à 15% de matière active. (2) L'épair est mesuré en continu à l'aide d'un appareil du Centre Technique des Papiers de Grenoble.

• . Bleached softwood kraft pulp (KBR) 45%
• . Bleached hardwood kraft pulp (KBF) 55%
• . CaCO ₃ charge
• . Load rate of finished paper 14%
• . Bonding (AKD) 0.15%
• . Cationic starch 0.6%

The tests carried out on the product obtained, under the conditions recorded in the Table below, lead to the results given in this table: RESULTS WAC Silica (1) Total retention Epair (2) Trial 1 ... 0 0.5% 58% 104 Trial 2 ... 1.65% 0 57% 70 Trial 3 ... 1.65% 0.15% 67% 72 (1) As a commercial product with 15% active material. (2) The air is continuously measured using a device from the Grenoble Technical Center for Papers.

Between test 1 and test 2, there is a very significant improvement in the air caused by the use of WAC instead of silica, a result consistent with what one skilled in the art expects. .

Test 3 shows the synergy that the association of small quantities of silica develops in the presence of WAC. At equivalent thickness, retention is increased by 10 points, ie an increase of 15 to 20%. This results in less pollution of the water in the circuits and greater ease of treatment of waste water at a lower cost.

Example 2 :

• . Vitesse machine   540 m/mn
• . Grammage   60 g/m²

The paper to be manufactured is printing-writing paper. The machine is identical to Example 1.

• . Machine speed 540 m / min
• . Weight 60 g / m ²

Fibrous composition :

• . KBR   40%
• . KBR   60%
• . Charges   CaCO₃
• . Taux de charge   11%
• . Amidon cationique   0,5%
• . Collage: colle AKD   0,15% (en produit commercial)

Les essais effectués sur le produit obtenu, dans les conditions consignées dans le Tableau ci-dessous, conduisent aux résultats donnés dans ce tableau: RESULTATS WAC Silice Rétention Epair Concentration en CDT (1) Essai 1 .. 1,6% 0 60% 76 8,4 g/l Essai 2 .. 1,5% 0,15% 73 75 6,5 g/l (1) CDT = caisse de tête

• . KBR 40%
• . KBR 60%
• . CaCO ₃ charges
• . Charge rate 11%
• . Cationic starch 0.5%
• . Bonding: 0.15% AKD glue (in commercial product)

The tests carried out on the product obtained, under the conditions recorded in the Table below, lead to the results given in this table: RESULTS WAC Silica Retention Epair CDT concentration (1) Test 1 .. 1.6% 0 60% 76 8.4 g / l Test 2 .. 1.5% 0.15% 73 75 6.5 g / l (1) CDT = headbox

Example 3 :

• . Vitesse   520 m/mn
• . Grammage   70 g/m²

The machine is the same as in Example 2

• . Speed 520 m / min
• . Weight 70 g / m ²

Fibrous composition :

• . KBR   35%
• . KBF   65%
• . Charge   CaCO₃
• . Taux de charge   14%
• . Amidon cationique   0,6%
• . Collage: colle AKD   0,15% (en produit commercial)

Les essais effectués sur le produit obtenu, dans les conditions consignées dans le Tableau ci dessous, conduisent aux résultats donnés dans ce tableau: RESULTATS WAC Silice Rétention Epair Concentration en CDT Essai 1 .. 1,5% 0 67% 75 8,7 g/l Essai 2 .. 1,5% 0,25% 78 76 7,2 g/l

• . KBR 35%
• . KBF 65%
• . CaCO ₃ charge
• . Charge rate 14%
• . Cationic starch 0.6%
• . Bonding: 0.15% AKD glue (in commercial product)

The tests carried out on the product obtained, under the conditions recorded in the Table below, lead to the results given in this table: RESULTS WAC Silica Retention Epair CDT concentration Test 1 .. 1.5% 0 67% 75 8.7 g / l Test 2 .. 1.5% 0.25% 78 76 7.2 g / l

Claims (13)

1. A process for manufacturing paper which comprises adding to the fibrous composition entering the head box:

   a) 5 to 30% of a mineral filler,

   b) 0.01 to 2% of a sizing agent, and

   c) a retention system characterised in that said retention system is comprised of:

   c)1) 0.2 to 1.7% of cationic starch having a molecular weight of 2.10⁴ to 2.10⁵ with a degree of substitution of 0.01 to 0.1;

   c)2) 0.01 to 0.3%, expressed as a percentage of Al₂O₃ of a polyaluminum chloride, and

   c)3) 0.01 to 0.3%, expressed as a percentage of SiO₂, of a silica sol of anionic nature, excluding aluminate ion surface modified silica sol in an Si/Al surface group ratio of 9.5:0.5 to 7.5:2.5.
2. The process for making paper according to claim 1, characterised in that the polyaluminum chloride is selected from the group comprising the salts of formulae I, II, III, and IV below and mixtures thereof: $${\text{Al}}_{\text{n}}{\text{(OH)}}_{\text{m}}{\text{CL}}_{\text{3n-m}}$$

   

      in which m and n are positive integers and 3n-m is positive; said salt being further able to contain a polyvalent anion Y selected from the anions of sulfuric, phosphoric, polyphosphoric, silicilic, chromic, carboxylic, and sulfonic acids, the molar ratio Y/Al being comprised in the range 0.015 and 0.4;
   
           Al_n(OH)_mCL_3n-m-2k(SO₄)k     (II)
   
      in which k, m and n are positive integers and 3n > m + 2k, the basicity m/3n is comprised between 0.3 and 0.7 and k/n = 0.01 to 0.03;
   
           [Al_n(HO)_3n-m-2pCl_m(SO₄)_p]z     (III)
   
      in which (3n-m-2p)/3n = 0.4 to 0.7; p = 0.04 to 0.25n; m/p = 8 to 35, k, m, n and p are integers and z is at least 1;
   
           Al_nOH_m(SO₄)_kCl_3n-m-2k     (IV)
   
      in which the basicity (m/3n)100 is comprised between about 40% and about 65% and has an Al equivalent/Cl equivalent ratio comprised between 2.8 and 5, apparent molecular mass MA measured by conventional light diffusion and apparent hydrodynamic diameters ØZ and ØW measured by quasi-elastic light diffusion of the following values:

   MA = 7000-35000

   ØZ (Å) = 350-2500

   ØW (Å) = 200-1200
3. The process according to claim 2, characterised in that the polyaluminum chloride is polychlorosulfate of aluminum of formula
   
           Al_nOH_m(SO₄)_kCl_3n-m-2k
   
   
4. A process according to claim 3, characterised in that said polyaluminum chloride is WAC having 10% Al₂O₃.
5. A process according to any one of claims 1 to 4, characterised in that the mineral filler is selected from clay, calcium carbonate, titanium dioxide, talc, hydrated alumina, and mixtures thereof.
6. A process according to claim 5, characterised in that the mineral filler is CaCO₃.
7. A process according to any one of claims 1 to 6, characterised in that the mineral filler is present in an amount of from 10 to 25% by weight based on the weight of said composition.
8. A process according to any one of claims 1 to 7, characterised in that the sizing agent is selected from the group comprising: alkyl ketene dimers (AKD), fluorinated phosphates, and carboxylic acid anhydrides, styrene/maleic anhydride, copolymers and derivatives and mixtures thereof.
9. A process according to claim 8, characterised in that the sizing agent is AKD.
10. A process according to any one of claims 1 to 9, characterised in that the cationic starch has a molecular weight of 3.10⁴ to 12.10⁴.
11. A process according to any one of claims 1 to 10, characterised in that there is added to said fibrous composition an optional component selected from polyethylene imines, carboxymethyl cellulose, urea-formol resins, melamin-formol resins, aminopolyamide-epichlorhydrine resins, polyamide-epichlorhydrine resins and mixtures thereof.
12. A process according to any one of claims 1 to 9, characterised in that the components added are:

    a) from 5 to 30% of CaCO₃,

    b) from 0.01 to 1% of AKD, and

    c)1 from 0.2 to 1.7% of cationic starch of molecular weight 2.10⁴ to 12.10⁵ and a degree of substitution of from 0.01 to 0.1 ; c)2 from 0.1 to 3% of WAC as 10% Al₂O₃ commercial product; and c)3 from 0.01 to 0.3% of silica sol, expressed as % of SiO₂.
13. A paper obtained by the process according to any one of the above claims.