EP0285487B1 - Paper making processes - Google Patents

Abstract

Papermaking process characterised in that the following are added to the suspension containing the cellulose fibres before the sheet is formed: calcium carbonate, a sizing agent such as a dimeric alkylketene or a carboxylic acid anhydride, cationic starch and a basic aluminium polychlorosulphate.

Description

The present invention relates to a process for making paper.

The raw paper pulp consisting essentially of cellulose fibers is put in 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 after the filter cloth.

The present invention relates more particularly to the products which are added before the sheet is formed. This is how mineral fillers are added such as calcium carbonate, titanium dioxide, etc. These fillers make the sheet of paper opaque which facilitates writing and printing. A bonding agent is also added to make the sheet resistant to liquids, that is to say that the bonded sheet of paper can be used for writing and printing. It is also necessary to add a retentive system which precipitates the bonding agent on the cellulose fibers and which also allows the retention of mineral fillers in the paper sheet.

The retentive system is often a mixture of several products. We also add products to improve the mechanical qualities of paper, dyes, etc.

All these products that we add do not have a well-defined action on a single characteristic of the paper but act more or less jointly and on several parameters. When using acid-sensitive fillers, for example calcium carbonate, it is important that the sizing agent and the retention system do not lead to an acidic aqueous suspension which causes decomposition of the carbonate and foams.

Often products and especially calcium carbonate are coated on the paper sheet. Part of the coated paper can also be recycled at the start of production, before the formation of the sheet which brings carbonate into the suspension before the paper machine even if we put other charges than carbonate in the suspension. This is why it is preferred to use bonding agents and retentive systems which do not lead to an acid suspension, this is called bonding in a neutral medium.

The article "papermaking additives", pages 803 to 825, volume 16 of the 3rd edition of KIRK OTHMER ed John Wiley 1981, described on pages 811-812 of bonding agents of the family of dimeric ketene alkyls usable in neutral medium, but does not specify the retention system.

The patent application under Japanese priority 85 JP 031519 of February 21, 1985 speaks of a collage in a neutral medium. The filler is calcium carbonate, poly aluminum chloride and a high molecular weight retention agent are added.

Patent GB 2 015 614 describes processes for manufacturing paper and cardboard in which a basic aluminum polychlorosulfate is added to the suspension before the sheet is formed. But either one does not stick, or one uses collophane, and one knows that the rosin must be used in acid medium, see KIRK OTHMER already quoted, page 810.

• a) une charge minérale,
• b) un agent de collage,
• c) de l'amidon cationique,
• d) du polychlorure d'aluminium.

We have now found an improvement in the papermaking processes, characterized in that the suspension containing the cellulose fibers is added, before the sheet is formed:

• a) a mineral filler,
• b) a bonding agent,
• c) cationic starch,
• d) poly aluminum chloride.

The suspension containing the cellulose fibers can be raw or bleached pulp, or a mixture of raw pulp and bleached pulp, or a pulp already containing additives.

The mineral filler can be any one or more products, preferably chosen from clay, calcium carbonate, silica, hydrated alumina, talc, titanium dioxide, etc.

These products are introduced in finely divided form or in the form of a paste or solution in the suspension. It is preferred to use calcium carbonate. The amount of carbonate can be any, and often is at most 40 parts per 100 parts of cellulose fibers, and preferably between 10 and 25. This quantity does not take not taking into account the charges contained in the recycled paper at the start of production in the suspension.

Although any bonding agent can be used, an agent which is used in a neutral environment is preferred.

Advantageously, the sizing agent can be a mixture of one or more products chosen from dimeric ketene alkyls and their derivatives, fluorinated phosphates, anhydrides of fatty chain carboxylic acids, certain polyurethanes, styrene maleic anhydride copolymers.

It is preferred to use dimeric ketene alkyls and carboxylic acid anhydrides. The quantity to be used depends on the desired properties of the paper. Advantageously, the amount is less than 10 parts per 100 parts of cellulose fibers, and preferably between 0.1 and 2 parts.

Cationic starch is a mixture of one or more products marketed under the generic name of cationic starch. These products are for example those described in KIRK OTHMER, 3rd edition, Vol. 21 page 503. The quantity is advantageously less than 5 parts per 100 parts of cellulose fibers and preferably less than 2.

• 1/ le sel de formule :
  
  dans laquelle n est quelconque, 3n-m est positif, m et n étant des nombres entiers positifs ; ledit sel pouvant contenir en outre un anion polyvalent Y choisi parmi les anions des acides sulfuriques, phosphorique, polyphosphorique, silicique, chromique, carboxylique, et sulfoniques, le rapport molaire
  
  étant de préférence compris entre 0,015 et 0,4.
• 2/ le sel de formule : $${\text{Al}}_{\text{n}}{\text{(OH)}}_{\text{m}}{\text{Cl}}_{\text{3n-m-2k}}{\text{(SO₄)}}_{\text{k}}$$
  
  dans laquelle k, m et n sont des entiers positifs, 3n > m + 2k, la basicité m/3n est comprise entre 0,3 et 0,7 et k/n = 0,01 à 0,3. Ce produit peut être préparé selon le procédé décrit dans le brevet US 3 929 666 ;
• 3/ le sel de formule :
  
  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 le brevet GB 2 128 977 ;
• 4/ le chlorosulfate d'aluminium basique de formule :
  
  dans laquelle la basicité ou le rapport molaire $$\frac{\text{m}}{\text{3n}}\text{x 100}$$
  
  est compris entre 40 % environ et 65 % environ et en ce qu'il 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 ⌀Z et ⌀W mesurés par diffusion quasi-élastique de la lumière de valeurs suivantes :
        MA = 7000 - 35000
        ⌀Z (Å) = 350 - 2500
        ⌀W (Å) = 200 - 1200
  Ce produit est décrit dans le brevet français FR 2 584 699.

Poly aluminum chloride designates the products that are usually called "poly aluminum chloride", "basic aluminum polychloride", "basic aluminum polychloride", and preferably one or more of the following products:

• 1 / the salt of formula:
  
  in which n is arbitrary, 3n-m is positive, m and n being positive integers; said salt possibly containing a polyvalent anion Y chosen from anions of sulfuric, phosphoric, polyphosphoric, silicic, chromic, carboxylic and sulfonic acids, the molar ratio
  
  preferably being between 0.015 and 0.4.
• 2 / the salt of formula: $${\text{Al}}_{\text{not}}{\text{(OH)}}_{\text{m}}{\text{Cl}}_{\text{3n-m-2k}}{\text{(SO₄)}}_{\text{k}}$$
  
  in which k, m and n are positive integers, 3n> m + 2k, the basicity m / 3n is between 0.3 and 0.7 and k / n = 0.01 to 0.3. This product can be prepared according to the method described in US Patent 3,929,666;
• 3 / the salt of formula:
  
  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. This product is described in patent GB 2,128,977;
• 4 / the basic aluminum chlorosulfate of formula:
  
  in which the basicity or the molar ratio $$\frac{\text{m}}{\text{3n}}\text{x 100}$$
  
  is between approximately 40% and approximately 65% and in that it has an Al / Cl equivalent equivalent ratio between 2.8 and 5, an apparent molecular mass MA measured by conventional light scattering and apparent hydrodynamic diameters ⌀Z and ⌀W measured by quasi-elastic light scattering with the following values:
  MA = 7000 - 35000
  ⌀Z (Å) = 350 - 2500
  ⌀W (Å) = 200 - 1200
  This product is described in French patent FR 2,584,699.

The quantity of polychloride of aluminum to be used expressed in Al₂O₃ is advantageously less than 0.5 parts per 100 parts of cellulose fibers and preferably between 0.05 and 0.2 parts.

The products a to d are added separately or as a mixture, or partially mixed and in any order. However, it is preferable to add poly aluminum chloride after the others. It is also preferred that the poly aluminum chloride be added as close as possible to the headbox. Cationic starch and polychloride of aluminum are not qualified as retentive systems; as we have indicated above all the products added to the suspension before the formation of the paper sheet act together. The present invention consists in adding the products a to d in the suspension and the Applicant has found that the joint use of these products has numerous advantages. The present invention is particularly useful for the manufacture of paper bonded in a neutral medium. The process of the present invention makes it possible to load the paper with products sensitive to acids such as calcium carbonate.

Another advantage of the invention is good retention of the charges and consequently a large reduction in the suspended matter in the waters obtained during the formation of the sheet.

Another advantage of the invention is greater productivity of the paper machine and better internal cohesion. All these advantages will appear in the examples.

Can also be added to the suspension of cellulose fibers, before the formation of the sheet and in addition to products a to d , other products such as dyes, mechanical reinforcing agents of the sheet.

According to another embodiment of the invention, products a to d can be added in addition to one or more products chosen from polyacrylamides, poly (ethyleneimines), carboxymethylcellulose, urea-formaldehyde resins, melamine-formaldehyde resins, aminopolyamide-epichlorohydrin resins, polyamide-epichlorohydrin resins. Advantageously, these products are used in addition to the cationic starch and in the same quantities.

The following examples illustrate the invention:

EXAMPLE 1 (not in accordance with the invention)

• Composition de la suspension aqueuse, avant la formation de la feuille, dite "composition en caisse de tête" :
  
• Caractéristiques de fonctionnement de la machine :
      Table plate, laize utile 3,5 m
      Grammage du papier : 180 g/m²
      Nature du papier : support de couche, puis enduction à la presse d'amidon dextrinifié ou enzymé ou oxydé.
• On ajoute de l'amidon cationique (0,3 partie pour 100 parties de fibres) et 420 g/tonne de fibres de poly(éthylèneimine).
• On obtient une vitesse de production de 207 m/mn, une rétention des charges de 77 %, une rétention totale de 92 %.

Manufacture of paper for printing and writing intended to be coated.

• Composition of the aqueous suspension, before the sheet is formed, known as the "headbox composition":
  
• Machine operating characteristics:
  Flat table, useful width 3.5 m
  Paper weight: 180 g / m²
  Nature of the paper: layer support, then press-coating of dextrinified or enzymatic or oxidized starch.
• Cationic starch (0.3 parts per 100 parts of fibers) and 420 g / tonne of poly (ethyleneimine) fibers are added.
• A production speed of 207 m / min is obtained, a charge retention of 77%, a total retention of 92%.

The internal cohesion, measured by the so-called "pendulum" device, is 87. The pendulum device used is the INTERNAL BOND IMPACT TESTER MODEL B supplied by GCA / PRECISION SCIENTIFIC, 3737 W. Cortland street, CHICAGO, USA.

The pH of the suspension during the formation of the sheet is 7.4.

The suspended solids (MES) in the clarified return waters are 170 mg / l.

EXAMPLE 2 (according to the invention)

The procedure is as in Example 1, but instead of poly (ethyleneimine), an aluminum polychloride of formula (II) is added in an amount of 0.1 part (expressed as Al₂O₃) per 100 parts of cellulose fibers.

A production speed of 221 m / min is then obtained, a charge retention of 86%, a total retention of 95.5%.

The internal cohesion becomes 110, the SS in the clarified return waters 100 mg / l and the pH in the headbox 7.3.

Despite its acidic nature, polychloride of aluminum keeps the medium in the pH zone compatible with the use of calcium carbonate. It provides a total retention gain of 3.5 points and charge retention of 9 points. The machine speed could be increased by 7%. The content of suspended matter in canvas water has decreased significantly. There is a gain in internal cohesion.

EXAMPLE 3 (not in accordance with the invention)

• Composition in headbox:
  
• Machine operating characteristics:
  Double useful width canvas 2.7 m
  Weight: 60 g / m²
  Type of paper: Offset printing then coating of starch in the press.

0.4 part cationic starch is added per 100 parts of fibers and 400 g / tonne of polyacrylamide fibers of molecular weight greater than 10⁷.
We obtain :

EXAMPLE 4 (according to the invention)

The procedure is as in Example 3, but instead of polyacrylamide, poly aluminum chloride of formula (II) is used in proportion to 0.1 part expressed as Al₂O₃ per 100 parts of fiber.

We obtain :

EXAMPLE 5 (not in accordance with the invention)

• Composition in headbox:
  
• Machine operating characteristics:

Coating by starch coating with the press.

0.3 part cationic starch per 100 parts of fibers and polyacrylamide 300 g / T of fibers are added. We obtain :

EXAMPLE 6 (according to the invention)

The procedure is as in Example 5 but less polyacrylamide is introduced, 100 g / T instead of 300 g / T, and a poly aluminum chloride of formula (II) is added in proportion to 0.1 part expressed as Al₂O₃ per 100 parts of fiber.

The following results are obtained:

Claims (8)

1. Process for the manufacture of paper in which the following are added to the suspension containing the cellulose fibres, before the sheet formation:

a) an inorganic filler,

b) a sizing agent chosen from dimeric alkylketenes and/or their derivatives and/or the anhydrides of carboxylic acids containing a fatty chain,

c) cationic starch,

d) aluminium polychloride.

2. Process according to Claim 1, characterised in that d is a basic aluminium polychlorosulphate.

3. Process according to Claim 1 or 2, characterised in that a is calcium carbonate.

4. Process according to one of Claims 1 to 3, characterised in that the quantity of a is less than 40 parts per 100 parts of cellulose fibres and preferably between 10 and 25.

5. Process according to one of Claims 1 to 4, characterised in that the quantity of b is less than 10 parts per 100 parts of cellulose fibres and preferably between 0.1 and 2.

6. Process according to one of Claims 1 to 5, characterised in that the quantity c is less than 5 parts per 100 parts of cellulose fibres and preferably less than 2.

7. Process according to one of Claim 1 to 6, characterised in that the quantity d expressed as Al₂O₃ is less than 0.5 parts per 100 parts of cellulose fibres and preferably between 0.05 and 0.2.

8. Process according to one of Claims 1 to 7, characterised in that the products a to d are supplemented by at least one product chosen from polyacrylamides, poly(ethylenediamine)s, carboxymethyl cellulose, urea-formaldehyde resins, melamine-formaldehyde resins, aminopolyamide-epichlorohydrin resins and polyamide-epichlorohydrin resins.