FI94971B - Method of production of packaging paper and cardboard or paperboard - 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

94971 *

Method of production of wrapping paper and paperboard or paperboard -Förfarande för framställning av omslagspapper och Papp eller karton

The present invention relates to a method for producing paper and more particularly to packaging paper and cardboard or paperboard.

The raw paper pulp, which consists mainly of cellulosic fibers, is placed in the form of a dilute aqueous suspension which is conveyed to the headbox of a paper machine, from where it is distributed on a filterable fabric on which a sheet of paper is formed. This sheet is then centrifuged and then dried. The qualities and properties of the paper obtained are determined precisely by the operating conditions of the paper machine, the raw pulp, the various additives added to the suspension before sheeting and also the substances to be coated after the fabric to be filtered on the paper sheet.

In particular, this invention relates to materials that are added prior to sheet formation.

The main feature required of a package is its durability, but it may be advantageous to make the paper also moisture resistant. The cellulosic fibers come from raw paper pulp, but often from recycled papers or cardboard, which are sometimes mixed into the raw pulp.

GB Patent 2,015,614 discloses a method of making packaging paper and corrugated board in which cationic starch and basic aluminum polychlorosulfate or aluminum sulfate are added to a fiber suspension prior to a headbox. The amount of cationic starch does not exceed 0.4% by weight based on the cellulose fibers. It is known that cationic starch contributes to the mechanical strength of the paper and it would be advantageous if it could be added to a suspension of much more than 0.4% and, above all, if this starch could be retained in the formed sheet.

But the starch is very hydrophilic and if the amount of 0.5% is exceeded, it is no longer possible to form a sheet of paper on the fabric to be filtered unless the productivity of the paper machine is greatly reduced. According to the present invention, a new method has been invented which makes it possible to use amounts of more than 0.5% of starch in the headbox of a paper machine.

The present invention is a process for the production of packaging paper and cardboard or paperboard, the process being characterized by adding to the suspension containing cellulose fibers before the sheet formations: a) more than 0.5 parts by weight of cationic starch per 100 parts of cellulose fibers, b) glue a substance selected from dimeric alkyl glycene dimers and carboxylic acid anhydrides, and c) less than 1 part by weight of aluminum polychloride expressed as Al 2 O 3 per 100 parts of cellulose fibers.

The suspension containing cellulosic fibers may be raw pulp or bleached pulp or a mixture of raw pulp and bleached pulp. Very often used papers and cardboards are added to the above mixture.

Cationic starch is a mixture of one or more substances, *; sold commercially under the generic name cationic starch. These materials are described, for example, in Kirk Othmer, 3rd edition, part 21, page 503. The amount is preferably between 0.5 and 5 parts per 100 parts of cellulose fibers, and more preferably between 0.7 and 2.

Aluminum polychloride means compounds commonly referred to as "aluminum polychloride", "basic aluminum polychloride", "basic aluminum polychlorosulphate" and in particular one or more of the following compounds: 1) a salt of the formula:

Al „(OH) mCl3n_m (I) i N i join i t i a.

3,94971 where n is any number, 3n-m is a positive Luka and m and n are positive integers; said salt may further contain a polyvalent anion Y selected from the anions of sulfuric acid, phosphoric acid, polyphosphoric acid, silicic acid, chromic acid, carboxylic acids and sulfonic acids, and the molar ratio Y is preferably between 0.015 and 0.4.

OH

2) a salt of the formula;

Ai (° H) Cl.-91f (SO 2). (II) nm 3n-m-2k 4 k where 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 - 0 , 3.

This compound can be prepared according to the method described in U.S. Patent 3,929,666; 3) a salt of the formula: (1n10H) 3n-m-2pcl ,, (SO 4> p] * f111 'where (3n-m-2p) / 3n = 0.4 to 0.7, p = 0.04 - 0.25n; m / p = 8-35; k, m, n and p are integers and z is at least 1. This compound is described in GB Patent 2,128,977; 4) basic aluminum chlorosulphate of the formula: A1 OH (SO.). Cl-, OL. (IV) nm 4 k 3n-m-2k where the basicity or molar ratio m_ x 100 is between about 40% and 3n about 65% and has an Al-equivalent / Cl-equivalent ratio between 2.8-5, apparent molecular weight MA measured by classical light diffusion and the apparent hydrodynamic diameters 0Z and 0W measured by the seemingly elastic diffusion of light are as follows: 4 94971 MA = 7000 - 35000 0Z (A) = 350 - 2500 0W (A) = 200 - 1200 This compound is described in the FR patent 2,584,699.

The amount of aluminum polychloride to be used, expressed as N 2 O 2, is preferably less than 1 part per 100 parts of cellulose fibers, and more preferably between 0.02 and 0.3 parts.

Although compounds a and b could be added in any order and at any location before the headbox of the paper machine, it is preferred to add aluminum polychloride after cationic starch. It is also considered best to add aluminum polychloride as close to the headbox as possible.

Other substances such as dyes may also be added to the cellulosic fiber suspension prior to sheet formation and in addition to compounds a and b.

According to another embodiment of the invention, in addition to the cationic starch, one or more substances selected from polyacrylamides, polyethyleneimines, carboxymethylcellulose, urea-formaldehyde resins: melamine-formaldehyde resins, aminopolyamide-epichlorohydride may be added. These substances are preferably used in addition to cationic starch and in the same amounts.

Likewise, according to another embodiment of the invention, in addition to compounds a and b or substances added with cationic starch, such as polyacrylamides and the other mentioned above, an adhesive can be added to make the paper slightly hydrophobic, which makes it resistant to moisture.

* 5 94971 Although any adhesive is suitable, collophan or a mixture of one or more substances selected from dimeric alkyl ketenes and their derivatives, fluorophosphates, carboxylic acid anhydrides with a fatty acid chain, some polyurethanes / maleic anhydride, styrene is preferably used. .

Preferably dimeric alkyl ketenes and carboxylic acid anhydrides are used. The amount used depends on the desired properties of the paper and cardboard or board. The amount is preferably less than 10 parts per 100 parts of cellulose fibers, and more preferably between 0.1 and 2 parts.

The adhesive is preferably added before the aluminum polychloride.

Conventional additives such as dyes, etc. can also be added to the suspension before sheeting.

One of the advantages of the invention, in addition to the good mechanical properties obtained, is the strong reduction of suspended solids in the waters recovered from under the fabric to be filtered during sheet formation.

The essential features of the invention are set out in the appended claims.

The invention also has the advantage of higher productivity and better internal cohesion of the paper machine. All these advantages emerge from the examples. The following examples illustrate the invention.

Example 1 • 1 (not according to the invention) - Composition contained in a headbox: 100% old papers

Adhesive: 0.15 parts of dimeric alkyl ketene.

- Typical characteristics of paper machine operation:

Useful width of flat surface: 2.6 m 94971 2 6

Surface pressure »: 190 g / m

Paper quality: corrugated board coating Treatment after sheet formation: dusting of natural starch on the surface.

1.4 parts of cationic starch are added per 100 parts of fiber.

Machine speed: 163 m / min

Total retention: 79%

Burst index Mullen: 2.75 (according to Afnor NF Q 03053).

pH (in the headbox): 7.2.

Example 2 (according to the invention)

Work as in Example 1, but add before the headbox aluminum polychloride in a ratio of 0.15 parts, expressed as Al 2 O per 100 parts of cellulose fibers.

This gives:

Machine speed: 200 m / min

Total retention: 85%

Mullen: 3.09 pH (in the headbox): 7.2.

Example 3 (according to the invention)

Work as in Example 2, but add 0.16 parts of aluminum polychloride, as in Example 2, per 100 parts of cellulose fiber to obtain:

Machine speed: 220 m / min

Total retention: 85%

Mullen: 2.96 pH (in the headbox): 7.2.

Claims (6)

A process for making wrapping paper and cardboard or paperboard, characterized in that the suspension containing the cellulose fibers prior to forming the sheet is added: a) more than 0.5 parts by weight of cationic starch per 100 parts of cellulose fibers, b) adhesives selected from dimeric alkyl ketene dimers and carboxylic acid anhydrides. c) less than 1 part by weight of aluminum polychloride expressed in Al2 O3 per 100 parts cellulose fiber. Process according to claim 1, characterized in that b is a basic aluminum polychlorosulfate. Method according to claim 1 or 2, characterized in that the quantity of a is preferably between 0.5 and 5 parts per 100 parts cellulose fibers and heist between 0.7 and 2. Process according to any one of claims 1-3, characterized in that the quantity of b expressed in A1203 is between 0.02 and 0.3 parts by weight per 100 parts of cellulose fibers. Process according to any of claims 2-4, characterized in that the quantity of sizing agent is preferably less than 10 parts per 100 parts cellulose fibers and heist between *: 0.1 and 2 parts. Process according to any one of claims 1-5, characterized in that in addition to a and £ or in addition to a and b and a sizing agent is added at least one substance selected from polyacrylamides, polyethylenimines, carboxymethyl cellulose, urea-formaldehyde resins, melamine-formaldehyde resins , aminopolyamide epichlorohydrin resins and polyamide epichlorohydrin resins. il: f KID I in S # *: