EP0285486B2 - Process for producing packaging paper and board - Google Patents

Abstract

1. Process for the manufacture of wrapping paper and of cardboard, characterized in that the following are added to the suspension containing the cellulose fibres before the sheet is formed : a) more than 0.5 parts by weight of cationic starch per 100 parts of cellulose fibres, b) less than 1 part by weigth, expressed as Al2 O3 , of aluminium polychloride per 100 parts of cellulose fibres.

Description

The present invention relates to a process for manufacturing paper and more particularly packaging paper and cardboard.

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 after the filter cloth.

The present invention relates more particularly to the products which are added before the sheet is formed.

The main quality sought for packaging is solidity, it can also be interesting to make paper resistant to humidity. Cellulose fibers come from raw pulp but often from recycled paper or cardboard, sometimes mixed with raw pulp.

British patent GB 2,015,614 describes a process for manufacturing wrapping paper and cardboard grooves in which cationic starch and a basic aluminum polychlorosulfate are added to the fiber suspension before the headbox. , or aluminum sulfate. The amount of cationic starch does not exceed 0.4% of the weight of cellulose fibers. It is known that cationic starch contributes to the mechanical resistance of the paper and it would be useful to be able to put much more than 0.4% in the suspension and above all to retain this starch in the sheet formed. Starch is very hydrophilic and if we exceed an amount of 0.5% we can no longer form the sheet of paper on the filter cloth except by greatly reducing the productivity of the paper machine. According to the present invention, a new process has been found which makes it possible to use amounts of starch greater than 0.5% in the headbox of the paper machine.

• a) plus de 0,5 partie d'amidon cationique pour 100 parties de fibres de cellulose,
• b) de 0,02 à 0,3 parties en poids de polychlorure d'aluminium exprimé en Al₂O₃ pour 100 parties de fibres de cellulose, l'amidon cationique et le polychlorure d'aluminium étant ajoutés à la suspension juste en amont de la caisse de tête, l'amidon cationique étant ajouté en premier juste avant l'ajout de polychlorure d'aluminium.

The present invention is a process for manufacturing wrapping paper and cardboard, characterized in that the suspension is added containing the cellulose fibers before the sheet is formed:

• a) more than 0.5 part of cationic starch per 100 parts of cellulose fibers,
• b) from 0.02 to 0.3 parts by weight of polychloride of aluminum expressed as Al ₂ O ₃ per 100 parts of cellulose fibers, the cationic starch and the polychloride of aluminum being added to the suspension just upstream from the headbox, the cationic starch being added first just before the addition of poly aluminum chloride.

The suspension containing the cellulose fibers can be raw or bleached pulp, or a mixture of raw pulp and bleached pulp. Very often we add used paper and cardboard to the previous mixture.

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 amount is advantageously between 0.5 and 5 parts per 100 parts of cellulose fibers, and preferably between 0.7 and 2.

• 1/ le sel de formule :
  
          Al_n(OH)_mCl_3n-m     (I)
  
  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, phosphoriques, polyphosphoriques, siliciques, chromique, carboxyliques et sulfoniques, le rapport molaire $\frac{\text{Y}}{\text{Al}}$
  
  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, 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 :
  
          [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 le brevet GB 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 $\frac{\text{m}}{\text{3n}}$
  
  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 0̸Z et 0̸W mesurés par diffusion quasi-élastique de la lumière de valeurs suivantes : $$\text{MA = 7000 - 35000}$$
  
  $$\text{0̸Z (Å) = 350 - 2500}$$
  
  $$\text{0̸W(Å) = 200 - 1200}$$
  
  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:
  
  Al _n (OH) _m Cl _3n-m (I)
  
  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 $\frac{\text{Y}}{\text{Al}}$
  
  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, 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:
  
  [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 patent GB 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 $\frac{\text{m}}{\text{3n}}$
  
  x 100 is between approximately 40% and approximately 65% and in that it has an Al equivalent / Cl equivalent ratio of between 2.8 and 5, an apparent molecular mass MA measured by conventional light scattering and apparent hydrodynamic diameters 0̸Z and 0̸W measured by quasi-elastic light scattering with the following values: $$\text{MA = 7000 - 35000}$$
  
  $$\text{0̸Z (Å) = 350 - 2500}$$
  
  $$\text{0̸W (Å) = 200 - 1200}$$
  
  This product is described in French patent FR 2,584,699.

Cellulose fibers can also be added to the suspension before the sheet is formed, and in addition to products a and b , other products such as dyes.

According to another embodiment of the invention, it is possible to add, in addition to the cationic starch, one or more products chosen from polyacrylamides, polyethyleneimines, carboxymethylcellulose, urea-formaldehyde resins, melamine-formaldehyde resins, resins aminopolyamide-epichlorohydrin, polyamide-epichlorohydrin resins. Advantageously, these products are used in addition to the cationic starch and in the same quantities.

It is also possible, according to another embodiment of the invention, in addition to the products a and b or in addition to the products which are added with cationic starch such as the polyacrylamides and others mentioned above, to add a sizing agent for make the paper a little hydrophobic allowing it to resist humidity.

Although any bonding agent is suitable, it is advantageous to use rosin or a mixture of one or more products chosen from dimeric ketene alkyls and their derivatives, fluorinated phosphates, fatty chain carboxylic acid anhydrides, certain polyurethanes, styrene / maleic anhydride copolymers.

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

Preferably the sizing agent is added before the poly aluminum chloride.

It is also possible to add to the suspension, before the sheet is formed, usual additives such as dyes, etc.

Another advantage of the invention, in addition to the good mechanical properties obtained, is a large reduction in the matter in suspension in the water collected under the filter cloth 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. The following examples illustrate the invention.

EXAMPLE 1 (not in accordance with the invention)

• Composition in headbox:
  • 100% old paper
  • Bonding agent: Alkyl ketene dimer 0.15 parts
• Operating characteristics of the paper machine:
  • Useful flat table width: 2.6 m
  • Weight: 190 g / m ²
  • Type of paper: cover for corrugated cardboard
  • Treatment after leaf formation: spraying of native starch on the surface.

• Vitesse machine : 163 m/mn
• Rétention totale : 79 %
• Indice d'éclatement Mullen : 2,75 (selon la norme afnor NF Q 03053)
• pH (en caisse de tête) : 7,2

Cationic starch, 1.4 parts per 100 parts of fiber, is added.

• Machine speed: 163 m / min
• Total retention: 79%
• Mullen burst index: 2.75 (according to afnor standard NF Q 03053)
• pH (in headbox): 7.2

EXAMPLE 2 (according to the invention)

The procedure is as in Example 1, but in addition, before the headbox, an aluminum polychloride is added in proportion of 0.15 parts expressed as Al ₂ O ₃ per 100 parts of cellulose fibers.

We obtain : Machine speed 200 m / min Total retention 85% Mullen 3.09 pH (in headbox) 7.2

EXAMPLE 3 (According to the invention)

The procedure is as in Example 2 but by adding 0.16 part of polychloride of aluminum counted in Example 2 per 100 parts of cellulose fibers, one obtains: Machine speed 220 m / min Total retention 85% Mullen 2.96 pH (in headbox) 7.2

Claims (8)

1. Process for the manufacture of wrapping paper and of cardboard, characterized in that the following are added to the suspension containing the cellulose fibres before the sheet is formed:

   a) more than 0.5 parts by weight of cationic starch per 100 parts of cellulose fibres,

   b) from 0.02 to 0.3 parts by weight of aluminium polychloride expressed as Al₂O₃ per 100 parts of cellulose fibres,

   the cationic starch and the aluminium polychloride being added to the suspension just upstream of the stuff-chest, the cationic starch being added first, just before the addition of the aluminium polychloride.
2. Process according to Claim 1, characterized in that a sizing agent is added, in addition to a and b.
3. Process according to Claim 1 or 2, characterized in that b is a basic aluminium polychlorosulphate.
4. Process according to one of Claims 1 to 3, characterized in that the quantity of a is between 0.5 and 5 parts per 100 parts of cellulose fibres.
5. Process according to one of Claims 1 to 4, characterized in that the quantity of a is between 0.7 and 2 parts per 100 parts of cellulose fibres.
6. Process according to one of Claims 2 to 5, characterized in that the sizing agent is chosen from alkyl ketene dimers and carboxylic acid anhydrides.
7. Process according to one of Claims 2 to 6, characterized in that the quantity of sizing agent is lower than 10 parts per 100 parts of cellulose fibres and is between 0.1 and 2 parts.
8. Process according to one of Claims 1 to 7, characterized in that, in addition to a and b or in addition to a and b and the sizing agent, at least one product is added, chosen from polyacrylamides, polyethyleneimines, carboxymethyl cellulose, urea-formaldehyde resins, melamine-formaldehyde resins, aminopolyamide-epichlorohydrin resins and polyamide-epichlorohydrin resins.