EP0334739A1 - Process for manufacturing papers and boards from recycled fibres which have been treated with enzymes - Google Patents

Abstract

Manufacture of papers and boards with the aid of a papermaking machine. …<??>According to the invention the machinability of a papermaking composition of recycled fibres is improved by a treatment of the fibre composition with the aid of an enzyme preparation producing an effect on all or part of the constituents of the cellulose fibres resulting in an improvement in the drainability of the water through the fibre mat.

Description

The present invention relates to the manufacture of paper or cardboard from recycled fibers.

The paper industry is increasingly using raw materials made from recycled fibers. With each recycling, the quality of the raw materials deteriorates and it is generally necessary to find a satisfactory level for the mechanical characteristics of the paper or cardboard produced, to subject the pulp to a refining.

The repercussions on sheet formation and the performance of the paper machine are significant. Above all, there is a decrease in the capacity for dripping water through the fibrous mat.

It is then necessary to increase the concentration of the fibrous suspensions in order to maintain a production rate comparable to the manufacture of sheets based on unbleached or bleached fibers for example.

The invention provides a method of manufacturing paper or cardboard using a paper machine, from at least one jet of an aqueous suspension of recycled fibers on the fabric of the paper machine, which allows increase the output of the paper machine, while allowing good sheet formation.

According to the process of the invention, the paper composition is made to act, essentially based on recycled fibers, before the at the end of the aqueous suspension of fibers on the canvas, an enzymatic preparation containing cellulases and / or hemicellulases and / or other enzymes having an action on all or part of the constituents of recycled cellulosic fibers which leads to an improvement in drainage , at a temperature between 15 and 80 ° C, at a pH between 3 and 8, for a period greater than 5 minutes and preferably between 10 minutes and 1 hour.

The action of enzymes on paper pulps has already been described in several patent publications.

We know for example from the French patent publication FR 2,557,894 a process for treating paper pulp with an enzymatic solution which promotes the refining of the pulp, that is to say which makes it suitable for being transformed into paper. having defined characteristics. According to this process, a particular enzymatic solution containing xylanases is made to act on an unrefined paste, having a fairly low Schopper-Riegler (SR) degree, of the order of 10.

This process therefore aims not to improve the drainage of the treated dough, but to improve its ability to refine.

Also known, from Canadian patent CA 758 488, is a process for refining a paper pulp which consists in subjecting an unrefined pulp to the action of an enzymatic solution based in particular on cellulase, pectinol or lipase, and on the simultaneously subject to mechanical refining. The aim is also to improve the refining of the treated pulp.

In the process according to the invention, the action of the enzymes is different. They act here on a pulp of recycled fibers which has poor machinability, due to poor drainability.

The action of the enzymes will result in an improvement in the drainability which will allow either a greater dilution of the paper composition in the headbox, or an increase in the speed of the machine and ultimately a gain in productivity, or both. The action of enzymes also results in an improvement in the mechanical characteristics of the sheet of paper, made from recycled fibers. It also results in that it allows the use as raw materials of a large percentage of fibers of very low categories, such as the category designated by wholesale store.

Thus, one aspect of the invention aims to provide a method for improving the machinability of a paper composition during the manufacture of a paper strip from a suspension of recycled fibers.

Another aspect of the invention aims to provide a process for manufacturing a paper from a composition of recycled fibers containing fibers of very low category in non-negligible percentage, which are normally incorporated at much lower rates in conventional papermaking processes, since they greatly penalize not only the drainability of the resulting fibrous suspensions, but also the mechanical properties of the papers produced from said fibrous suspensions.

Among all the enzymatic preparations containing cellulases and / or hemicellulases and others such as esterases, mananases, etc. which are used according to the invention, preferably those which have a C₁ activity, a C activity are chosen. _x and xylanasic activity.

These three activities are defined by the international nomenclature of enzymes and they can be qualified and expressed in units of the international system per milligram of powder of the enzyme preparation considered. The activity Cactivité is the action of cellobiohydrolase which can be assayed on very organized pure cellulose. This activity is manifested by the production of cellobiose and the international system has retained the AVICEL substrate as the reference substrate. The activity C _x is assayed on modified cellulose, carboxymethylcellulose for example and it is quantified by a fall in the viscosity of the carboxymethylcellulose or an increase in the reducing activities. The xylanasic activity allows hydrolysis of the binding xylans.

The enzyme preparation is used at an enzyme concentration which varies according to the C₁, C _x or xylanasic activities of the enzymes contained in the preparation. Thus, the enzymatic preparation is preferably used at a concentration of 0.01% to 2% of the weight of the dry dough, these percentages corresponding to a preparation having a C₁ activity of 0.168 USI per milligram of powder, an activity C _x of 3.9 USI per milligram of powder and a xylanasic activity of 31 USI per milligram of powder.

It goes without saying that the concentrations of the enzyme preparations can be adapted according to the type of preparation used. However, it generally remains with enzyme preparations whose activities have been described above, below a concentration equal to approximately 0.01% of the weight of the dry dough, no significant effect is observed, except to extend the reaction time until durations unsuitable for industrial production rates. at around 2% of the weight of the dry pulp, the cost of the operation tends to become prohibitive, and the mechanical characteristics of the paper produced tend to drop.

The reaction medium can be more or less suitable for the action of enzymes. Temperature and pH conditions are more particularly suitable for avoiding any risk of denaturation of the enzymes by the medium. The pH is thus between 3 and 8, and the temperature between 15 ° C and 80 ° C. Above 80 ° C, the medium tends to denature the enzyme, and below 15 ° C, the action of the enzymes manifests itself particularly slowly.

Rather than seeking to modify the reaction medium to adapt it to the action of enzymes, the process according to the invention advantageously proposes to adapt the enzymatic preparation to industrial operating conditions, generally used in stationery, that is to say without other modifications to the manufacturing process.

Other advantages and characteristics of the invention will appear in the following description of an exemplary embodiment.

Examples 1 to 15 demonstrate the action of enzymatic preparations on the drainability of paper compositions based on recycled fibers.

Examples 16 to 20 show the advantages and in particular the productivity gains provided by the invention on an industrial machine.

EXAMPLE 1 to 12

An aqueous suspension of paper pulp based on recycled fibers is prepared as follows:

Weigh 1 kg dry of a pulp made entirely of fibers from recycled cardboard boxes.

It is made into an aqueous suspension at 3% by weight, adding water to a total weight of 33.333 kg. The pH of the fibrous suspension is adjusted to the desired value, by adding either sulfuric acid (H₂SO₄, 1N) to obtain acidic pH, or sodium hydroxide (NaOH, 1N) to obtain basic pH. An advantageous way of proceeding is to control the pH using a pH meter when adding either the acid or the base, while homogenizing the fibrous suspension. Then the fibrous suspension is brought to the desired temperature rée. Once this temperature has been reached, 1.6 ml of an enzymatic solution based on cellulases and hemicellulases, marketed under the name Multifect L 250, by the company FINNISH SUGAR CO are introduced. The enzymes are allowed to react for a variable time according to the examples and the drainability of the paper suspensions is measured using the BRITT-JAR apparatus according to the protocol described below. Drainability is thus measured before the introduction of the enzymes and after the treatment.

To measure the drainability, a suspension of paper fibers is prepared at a concentration of 10 g / l and 650 ml of this suspension are taken and poured into the BRITT-JAR device which comprises a cylindrical body with a diameter of 10.2 centimeters at the base of which is a filter cloth of the same nature and characteristics as the cloth of the paper machine. This device is marketed for example by the company NOVIPRO. The volume of water which has passed through the fabric after 15 seconds under a vacuum of 0.2 bars, without stirring the aqueous suspension, is called draining (or drainability).

In this example, the measure of drainability before the introduction of enzymes is 320.

12 examples of treatments which are different from each other are thus produced, by temperature, pH or duration of the treatment. The conditions as well as the results are collated in Table 1 below.

EXAMPLES 13 to 15

The procedure is as in Examples 1, 5, 10 respectively, except that the enzymatic preparation of these examples is replaced by another preparation, namely an aqueous solution of a powder of Maxazyme CL 2000 sold by the French company RAPIDASE. TABLE 1 Ex. Temperature ° C pH reaction time in hours drainability after treatment 1 50 5 0.5 510 2 50 6 0.5 510 3 50 7 1 420 4 40 5 1 510 5 40 6 1 500 6 40 7 1 485 7 40 7.5 2 485 8 25 5 2 475 9 25 6 2 465 10 25 7 2 475 11 25 7.5 2 435 12 50 4 1 485 13 50 5 0.5 500 14 40 6 1 485 15 25 7 2 475

The examples show that the treatment of the suspension with enzymes provides an increase in the drainability of the fibrous suspension, which leads to a higher speed of drainage and therefore a better machinability.

EXAMPLE 16

In this example, we want to make paper for covering cardboard boxes with a grammage of 125 g / m², by using an industrial paper machine.

The starting fiber composition is made up of 95% by weight of boxes of salvage cardboard and 5% by weight of warehouse wholesale. Using a pulper, an aqueous suspension at 30 g / l is made of it continuously. This suspension then passes through the various standard purifiers and storage tanks. In the last of these vats, while the fiber suspension is at a temperature of 45 ° C and a pH of 6, an enzyme preparation based on cellulases and hemicellulases is introduced therein, at the rate of 1.2 liters. per dry ton of paper produced, of a solution sold under the name Multifect L 250 ™ by the company FINNISH SUGAR CO Ltd. It is left to react during the time of passage of the suspension in the vat which cor responds to approximately 30 minutes.

The suspension treated with enzymes is then sent to the headbox, where it is brought to a concentration of 7.4 g / l.

The composition is poured onto the canvas of the paper machine which moves at a speed of 250 m / min.

This produces 4.15 tonnes / hour of cover paper.

The burst index is measured in accordance with standard NFQ 03053. This index represents the quotient of the maximum pressure distributed uniformly, and supported by a test piece of paper, perpendicular to its surface, by the grammage of the paper. In this example we find a burst index of 1.79.

COMPARATIVE EXAMPLE 16

The procedure is as in Example 15, except that there is no enzyme treatment. The concentration in the headbox is 9.5 g / l so as to obtain the best compromise between correct drainability and maximum production. The production obtained is 3.89 tonnes / hour.

The burst index of manufactured paper is 1.64.

This comparative example highlights the advantages provided by the invention: greater dilution in the headbox and an increase in the speed of the machine, this gain results in a gain in productivity. There is also a gain in paper characteristics.

EXAMPLE 17

The procedure is as in Example 16, except that the concentration in the headbox is modified by keeping the same concentration as in Comparative Example 16, and by increasing the speed of the machine to bring it to 255 m / min. Production reaches 4.22 tonnes / hour.

The measured burst index is 1.65.

By comparison with comparative example 16, it is noted that the treatment with enzymes makes it possible to considerably increase the speed of the machine without losing the mechanical characteristics of the paper.

EXAMPLE 18

In this example, the procedure is as in Example 16, but the fibrous composition which is formed here is 80% of recycled cardboard boxes and 20% of warehouse bulk.

The headbox concentration is 8.5 g / l and the machine speed is 241.8 m / min.

The production of the machine, in paper, is 4.01 tonnes / h.

The measured burst index is 1.65.

By comparison with Comparative Example 16, it is noted that in addition to the production gain, it is possible to increase the quantity of wholesale store (lowest quality) and to decrease the cost of manufacturing paper while preserving satisfactory mechanical characteristics.

The action of the enzymes by improving the drainability of the fibrous suspension makes it possible to increase the dilution in the headbox and thus to improve the formation of the sheet.

EXAMPLE 19

A 190 g / m² cover paper is made from a fibrous composition of 80% box clippings and 20% good cardboard.

The procedure is as in Example 15 using an enzyme dosage of 0.9 l / tonne of dry product paper.

The headbox concentration is 8.6 g / l and the machine speed is 163.3 m / min. Paper production is 3.92 tonnes / hour.

The measured burst index is 2.33.

COMPARATIVE EXAMPLE 19

The procedure is as in Example 19, except that the paper composition is not treated with enzymes.

The concentration in the headbox for the best compromise between drainability and production is 10.5 g / l and the speed of the machine is 153.6 m / min. Paper production is 3.69 tonnes / hour and the burst index is 2.14.

This comparative example highlights the advantages obtained by the invention over the productivity and characteristics of paper with another starting papermaking composition. The treatment with an enzymatic preparation based on cellulase and / or hemicellulase makes it possible to dilute more strongly in the headbox, which provides better sheet setting, while increasing the speed of the machine.

EXAMPLE 20

We want to make a "Test liner" paper of 180 g / m².

We operate as in Example 16, but taking as com starting position 80% box clippings and 20% Krafts bags. The dosage of enzymes is 0.65 l / tonne of paper produced.

The headbox concentration is 8.5 g / l and the machine speed 152.3 m / min.

Paper production is 3.78 tonnes / hour.

The measured burst index is 2.84.

COMPARATIVE EXAMPLE 20

The procedure is as in Example 20, except that the paper composition is not treated with enzymes.

The concentration in the headbox for the best compromise between drainability and production is 10.2 g / l and the machine speed is 151.4 m / min. Paper production is 3.61 tonnes / hour and the burst index is 2.75.

The advantages described above are found in example 20.

Claims (7)

1. Method for manufacturing paper or cardboard from a paper composition essentially based on recycled fibers by using a paper machine with the deposition of at least one jet of an aqueous suspension of the fibers on a canvas , characterized in that before the suspension is deposited on the canvas, the paper composition is treated using an enzymatic preparation containing cellulases and / or hemi-cellulases and / or other enzymes having an action on all or part of the constituents of the cellulosic fibers, which leads to an improvement in the drainability, at a temperature between 15 and 80 ° C and at a pH between 3 and 8, for a duration greater than 5 minutes and preferably included between 10 minutes and 1 hour. 2. Method for improving the machinability of a paper composition based essentially on recycled fibers, characterized in that the paper composition is treated with an enzymatic preparation resulting in an improvement in the drainability of the water through the fibrous mattress, without other modifications of the manufacturing process. 3. Method according to claim 2, characterized in that the enzymatic preparation contains cellulases and / or hemi-cellulases. 4. Method according to one of claims 1 to 3, characterized in that the treated paper composition is formed from 100% recycled fibers. 5. Method according to one of claims 1 to 4, characterized in that the paper composition of recycled fibers comprises from 0 to 25% of recycled fibers of the lowest category. 6. Method according to one of claims 1 to 5, characterized in that the enzymatic preparation is used in an amount of 0.01% to 2% by weight of the dry dough. 7. A method for improving the mechanical properties of the papers obtained by using a paper machine from a paper composition of recycled fibers, characterized in that the paper composition is treated using a enzymatic preparation improving drainability and making it possible to increase the dilution of the aqueous suspension of fibers in the headbox compared to the dilution corresponding to the best compromise drainability-production of the untreated paper composition.