EP2761081A1

EP2761081A1 - Enzymatic pretreatment of wood in a method for producing mechanical paper pulp

Info

Publication number: EP2761081A1
Application number: EP12767039.6A
Authority: EP
Inventors: Jérôme BLANC; Christophe Calais; Valérie MEYER; Michel Petit-Conil
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2011-09-30
Filing date: 2012-09-06
Publication date: 2014-08-06
Anticipated expiration: 2032-09-06
Also published as: US20140231034A1; CA2844380C; US9834886B2; FR2980805B1; FR2980805A1; CA2844380A1; EP2761081B1; WO2013045782A1; CN103842581A; CN108660826A

Abstract

The invention relates to a method for producing mechanical paper pulp comprising at least: a step in which unprocessed wood is impregnated, whereby unprocessed wood is exposed to an impregnating composition comprising at least a laccase enzyme and a formula mediator (I), in which R1 and R2 are identical or different groups, chosen from among a hydrogen atom, a hydrocarbon chain, linear or branched, saturated or unsaturated, comprising 1 to 14 carbon atoms, where each hydrocarbon chain can be replaced by one or more functional groups chosen from among -OH, -SO3, benzyl, amino, mercapto, keto or carboxyl, where R1 and R2 in combination can form a cyclical structure, to achieve impregnation of the wood; and a step in which the impregnated wood is mechanically refined, such that a mechanical paper pulp is obtained. The invention also relates to the impregnating composition used in this method and to the use thereof in a method for producing mechanical paper pulp, as well as to a method for producing paper.

Description

ENZYMATIC WOOD PRETREATMENT IN A PROCESS FOR PRODUCING MECHANICAL PAPER PULP

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing mechanical pulp. It also relates to a composition implemented during this process and to the use of this composition in a mechanical pulping process. Finally, it relates to a papermaking process.

TECHNICAL BACKGROUND

Paper pulps called "mechanical pulp" or "high-performance pulps" or "wood pulp" are obtained directly from the wood by a series of mechanical treatments, generally grouped under the name "mechanical refining", carried out by means of grinding wheels and / or refiners. The mechanical paper stock is then subjected to a bleaching phase which may comprise one or more stages depending on the degree of whiteness required.

The advantage of a mechanical pulping process is its high material yield, compared to a so-called "chemical" pulping process. Indeed, unlike chemical pulping processes in which the lignin present in the raw wood is eliminated almost completely by cooking in the presence of chemicals, about 90% of the raw wood is preserved in the pasta obtained in the pasta. from a process for manufacturing mechanical pulp.

Mechanical refining of a mechanical pulp manufacturing process typically involves several refining steps, such as primary refining generally referred to as "defibration", secondary refining, tertiary refining, refining of classification rejects, and the like. These refining steps provide pastes with different degrees of refinement, in order to gradually transform the wood into individualized fibers and thus enable the manufacture of paper pulp.

Mechanical refining has the disadvantage of being a major consumer of energy, typically from 1500 to 3000 kWh per ton of mechanical pulp produced. This energy represents on the one hand a significant cost and on the other hand, it is likely to damage the wood fibers. Also different ways have been considered to reduce the energy to bring. Thus, EP 1728917 proposes to carry out a low consistency refining, that is to say with a low dry matter content of pulp. However, such a treatment requires a large number of equipment and its effectiveness remains limited.

The document WO 08081078 proposes, for its part, a method for manufacturing mechanical paper pulp comprising an ozone treatment step during refining. However, this treatment has the disadvantage of creating chromophore groups on the polysaccharide molecules contained in the wood, which prove difficult to oxidize when conventional bleaching of the paste is then implemented.

In addition, there has been a particular interest in enzymatic wood treatments in mechanical pulping processes because of their low environmental impact.

US 6267841 discloses a process for manufacturing mechanical pulp comprising an enzymatic treatment step implemented between two refining steps or prior to a refining step. The enzyme is selected from pectinases, xylanases, laccases, cellulases, manganese peroxidases and mixtures thereof. However, these treatments have the disadvantage of degrading the wood fibers and / or require refining at a high temperature, which limits the energy saving achievable.

EP 429422 and WO 91/11552 also disclose processes for manufacturing mechanical pulp comprising an enzymatic pretreatment step of a fibrous material to facilitate subsequent refining. In EP 429422, the redox potential of the described enzymes is adjusted by means of regulators such as nitrogen or oxygen gas, antioxidants, sugars, organic acids or inorganic salts. In WO 91/11552, it is recommended to carry out the enzymatic pre-treatment below a certain redox potential. However, adjusting the redox potential of the enzymes is a delicate operation to implement and is expensive.

The document EP 0745 154 describes a method of manufacturing chemical pulp using a multi-component system for the modification, decomposition or decolorization of lignin, comprising in particular an oxidoreductase enzyme, a mediator, a free amine and a oxidizing agent. This system is used to whiten a chemical pulp previously delignified with oxygen. This system has the drawbacks of generating effluents that are harmful to the environment and to generate high production costs. The optimization of the enzymatic activity of laccases has moreover been studied in document US 2008/0189871. This document proposes an LMS (Laccase Mediator System) system comprising a mediator derived from 2,6-dimethoxyphenol. This system is implemented to whiten a fabric. It is mentioned, on the one hand, that it can be used during the manufacture of paper pulp and, on the other hand, that it can be used during the bleaching of a pulp.

Thus, the methods and products used in the state of the art are not entirely satisfactory.

In particular, there is still a need to reduce the energy demand of mechanical pulp manufacturing processes and to guarantee a mechanical paper pulp with equivalent or improved paper qualities, compared to those obtained by known methods. There is also a need for a mechanical pulp having a higher degree of whiteness at the end of refining and / or developing a better bleaching ability than those obtained by known methods. Finally, there is a need to reduce the amount of chemicals to be used for bleaching a mechanical pulp while maintaining an equivalent or improved degree of whiteness compared to the mechanical paper pulp obtained with the methods of the state of the art. the technique.

SUMMARY OF THE INVENTION

Also, the present invention relates to a method of manufacturing a mechanical paper stock to overcome the above drawbacks.

More specifically, the invention relates in the first place to a method of manufacturing a mechanical paper stock comprising at least:

a step of impregnating a raw wood comprising contacting the raw wood with an impregnating composition comprising at least one laccase enzyme and a mediator of formula (I):

Ri

\

In which R1 and R2 are identical or different groups chosen from a hydrogen atom, a linear or branched, saturated or unsaturated hydrocarbon-based chain comprising from 1 to 14 carbon atoms, each hydrocarbon-based chain possibly being substituted by one or more functional groups selected from -OH, -SO 3, benzyl, amino, mercapto, keto, carboxyl, where R 1 and R 2 may together form a ring structure (as in the piperidinyloxy compounds), to obtain an impregnated wood; and

a step of mechanical refining of the impregnated wood, so as to obtain a mechanical pulp.

More preferably, the process for manufacturing a mechanical paper pulp of the invention comprises at least:

wherein R1 and R2 are the same or different groups selected from a hydrogen atom or a C1-C8 alkyl chain, to obtain an impregnated wood; and

Among the mediators of formula (I), those for which at least one of R 1 and R 2 is different from H are furthermore preferred. Those for which R 1 = R 2 and R 2 are each a C 1 -C 8 alkyl radical, in particular C1-C6 and more preferably C1-C4. A particularly preferred example being N, N-diethylhydroxylamine.

The invention also relates to the impregnating composition used in this process.

The invention also relates to the use of said impregnating composition in a mechanical pulp manufacturing process for lowering the energy consumption of said process.

The invention further relates to the use of said impregnating composition in a process for manufacturing mechanical pulp to increase the whiteness of said paste.

The invention also relates to the use of said impregnating composition in a process for manufacturing mechanical pulp comprising a mechanical refining step, said impregnating composition being used before the mechanical refining step.

The invention finally relates to a papermaking process, comprising the manufacture of a mechanical paper pulp according to the method above, as well as the use of this mechanical paper pulp to produce paper.

The present invention overcomes the disadvantages of the state of the art. In particular, it provides a method of manufacturing mechanical pulp more energy-efficient and which guarantees a pulp and paper paper qualities equivalent or improved over known methods. It also provides a mechanical pulp having a higher degree of whiteness at the end of the refining and / or developing a better bleaching ability compared to mechanical pulps obtained with the known methods. The invention also makes it possible to reduce the quantity of chemicals to be used for laundering the mechanical paper stock, while guaranteeing a degree of whiteness at the end of the whitening at least equivalent to or even greater than that of mechanical paper stocks. produced with the known methods. This is accomplished by a wood impregnation step with a particular impregnating composition prior to refining.

In particular, the composition according to the invention oxidizes the phenolic and non-phenolic units of the lignin, which leads to weakening of the bonds between the fibers. The Applicant has in particular developed an impregnating composition that acts specifically on the cell wall of the fibers, to reduce the cohesion between the fibers while preserving them. Also, when the composition of the invention is used on a wood before refining, it reduces the energy that it would be necessary to provide during the refining to separate the wood fibers if no pretreatment was performed or if a state-of-the-art method was implemented in its place. In addition, the length of the fibers from the starting wood and their strength are preserved in the manufactured mechanical pulp and in the paper that is derived therefrom.

Finally, unlike the compositions proposed by the state of the art, the impregnating composition according to the invention is inexpensive, available in large quantities and less toxic to the environment.

DEFINITIONS

By "mediator" according to the invention is meant a compound which improves the ability of an enzyme to oxidize a wood.

By "wood" is meant all secondary resistant tissues (support, conduction, and storage) which form the trunks, branches and roots of woody plants, within the meaning of standard NF B 50-003.

By "raw" wood is meant the state of a wood before its treatment with an impregnating composition according to the invention and "impregnated" wood means the state of a wood after its treatment with an impregnating composition according to the invention.

Unless otherwise stated, the percentages of material mentioned are percentages by weight.

Unless otherwise stated, percentages by weight of wood are given by weight of dry wood. "Dry wood" means that the wood has been kiln-dried in accordance with ISO 638: 2008, ie at a temperature of between 103 ° C and 107 ° C, for a period of not less than 30 minutes and not exceeding not 16 hours at atmospheric pressure.

The "consistency" of mechanical pulp refers to the pulp concentration as defined in ISO Standard 4119 of June 1996. This is the ratio of the dry mass of filterable material to a suspended pulp sample, to the mass of the unfiltered sample, the test being carried out in accordance with said International Standard. The paste concentration is expressed as a percentage by mass.

Unless otherwise stated, percentages by weight of mechanical pulp are given by weight of dry mechanical pulp. By "dry mechanical paper pulp" is meant the dry mass of material of a suspended pulp sample as defined in the abovementioned ISO standard 4119, being measured after filtering and drying in accordance with said standard.

Unless otherwise specified, measurements are made at atmospheric pressure.

When referring to intervals, expressions of the type "from ... to" include the bounds of the range. On the other hand, expressions of the type "between ... and ..." exclude the bounds of the interval.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows.

In a schematic manner, the process for manufacturing mechanical pulp according to the invention comprises at least:

- A step of impregnating a raw wood, comprising contacting the raw wood with an impregnating composition according to the invention, so as to obtain an impregnated wood,

a step of mechanical refining of the impregnated wood, so as to obtain a mechanical pulp. In more detail, the process for manufacturing mechanical pulp according to the invention comprises, preferably in the order, the following steps:

- optionally a steaming of raw wood,

- possibly a pressing of a raw wood,

at least one step of impregnating a raw wood with an impregnating composition according to the invention, to obtain an impregnated wood,

- optionally steam steaming of the impregnated wood,

at least one step of mechanical refining of the impregnated wood, to obtain a mechanical pulp,

optionally a step of chelating the mechanical pulp,

possibly a bleaching of the mechanical paper stock.

Steps (optional ^') pretreatment of raw wood

Raw wood is used as raw material.

According to one embodiment, the raw wood is selected from softwoods, hardwoods or mixtures thereof. Suitable softwoods include Douglas fir, Spruce, Aleppo pine, Maritime pine, Black pine, Scots pine, Taeda pine, Red cedar (Thulya plicata) or mixtures thereof. Suitable hardwoods include poplar, aspen, birch, maple, oak, eucalyptus, acacia, beech, chestnut, hornbeam, alder or mixtures thereof. Preferably, spruce, poplar, eucalyptus or a mixture thereof is used.

According to one embodiment, in order to manufacture a chemomercomechanical pulp (CTMP), the raw wood may be chosen from softwoods such as those mentioned above, hardwoods such as those mentioned above, or bamboo, hemp, cereal straw, for example wheat straw or rice straw, cotton or mixtures thereof.

According to a preferred embodiment, the raw wood is in the form of chips. The term "chips" is used in the conventional sense for those skilled in the art. It designates wood particles that can be obtained by any industrial process conventionally used in the field of mechanical pulp. The chip size is typically distributable according to the standard SCAN-CM 40:01. This form facilitates the subsequent impregnation treatment of the wood and improves its effectiveness. The chips can typically be obtained from debarked and cut raw logs or residual by-products from the wood industry. According to one embodiment, the wood undergoes, before or after the impregnation step, preferably before the impregnation step, at least one pretreatment chosen from a heat pretreatment, a chemical pretreatment, a mechanical pretreatment or a combination of these. Suitable heat pretreatment include steam steaming, hot water treatment or a combination thereof. As a suitable chemical pretreatment, there may be mentioned a wood impregnation treatment with at least one chemical agent chosen from an acid, a base, an oxidant, a reducing agent, a chelator, a stabilizer, a surfactant, an enzyme or their mixtures. As suitable mechanical pretreatment, there may be mentioned a pressing.

According to one embodiment, the wood undergoes, before or after the impregnation step, preferably before the impregnation step, steam steaming, which makes it possible to homogenize the dryness of the wood. Stoving includes contacting the wood with water vapor. Steaming is preferably carried out at atmospheric pressure. Stoving preferably has a duration of from 5 to 30 minutes, more preferably from 10 to 20 minutes.

According to one embodiment, the raw wood undergoes, before or after the impregnation step, preferably before the impregnation step, a pressing. The pressing can be carried out using any means known to those skilled in the art, preferably with the aid of a compression device such as a screw press or a cylinder press.

The aforementioned embodiments may advantageously be combined with one another: according to a preferred embodiment, the raw wood is initially in the form of chips and the chips are steam-steamed as defined above; according to another preferred embodiment, the raw wood undergoes, before the impregnation step, a steam steaming followed by pressing as defined above.

According to a particular embodiment, the wood does not undergo chemical pretreatment before the impregnation step, in particular no acid wash or chelation treatment.

The various pretreatments mentioned above can be implemented before or after the impregnation stage. They can be repeated if needed. For example, one of these pretreatments can be implemented before the impregnation step, perform the impregnation step and then repeat said pretreatment after the impregnation step. Impregnation stage

The manufacturing method according to the invention comprises a step of impregnating a raw wood, comprising contacting the raw wood with an impregnating composition according to the invention so as to obtain an impregnated wood. Said impregnation composition comprises at least one laccase enzyme and a mediator of particular formula. The impregnating composition according to the invention thus comprises a mediator of formula (I):

in which R1 and R2 are identical or different groups chosen from a hydrogen atom or a C1-C8 alkyl chain.

Preferably, R 1 and R 2 are identical or different groups chosen from a hydrogen atom or a C 1 to C 4 alkyl chain. More preferably, R1 and R2 are identical or different C1 to C4 alkyl chains. More preferably, R1 and R2 are identical alkyl chains of formula C2H5: the preferred mediator is thus diethyl hydroxylamine (DEHA).

The mediator may be present in the impregnating composition in pure form, in solution in water or in the form of one of its salts.

The mediator content in the impregnating composition is preferably from 0.1% to 10% by weight, preferably from 0.15% to 4.5% by weight, preferably from 0.19% to 4% by weight. weight, preferably from 0.19% to 3% by weight, or even from 0.23% to 2% by weight relative to the total weight of the impregnating composition.

The mediator content, relative to the dry raw wood mass to be treated, is preferably from 0.1% to 10%, from 0.2% to 10%, from 0.2% to 5%, more preferably from 0.2% to 0.5%, or even 0.25% to 0.5%, by weight of dry wood.

The enzyme laccase may be selected from class EC 1.10.3.2 of the Enzyme Nomenclature. Myceliophthora laccase is particularly preferred.

The laccase enzyme may be in the form of a crude extract, in purified or semi-purified form.

The solution content of the laccase at 1000 LAMU / ml, relative to the dry raw wood mass to be treated, is preferably from 0.1 to 10 L / t, from 1 to 5 L / t, more preferably from 1 to 2 L / t of dry raw wood.

The solution content of 1000 LAMU / ml laccase in the impregnating composition is preferably from 0.01% to 10% by weight, from 0.05% to 5% by weight. weight, from 0.05% to 1% by weight, in particular from 0.09% to 0.2% by weight, relative to the total weight of the impregnating composition.

The impregnating composition according to the invention may further comprise one or more additives customary to the person skilled in the art, provided that their presence does not detract from the effectiveness of the composition. Such additives may especially be chosen from: an enzyme other than laccase, an oxidant, a reducing agent, an acid, a base, a chelating agent, a stabilizer, a surfactant, their combinations. When present, the total additive content in the impregnating composition is preferably less than 3% by weight, in particular less than 2% by weight, relative to the total weight of the composition. According to one embodiment, the impregnating composition does not comprise an additive.

According to one embodiment, the impregnating composition is an aqueous solution. The water content of the composition then corresponds to the complement at 100% by weight of the sum of the contents of mediator, enzyme and possible additives.

According to one embodiment, the impregnating composition is used at a rate of 0.1 to 12 L / kg of dry raw wood to be impregnated, preferably at a rate of 1 to 10 L / kg of the raw wood to be impregnated. The excess impregnating composition may advantageously be recycled to perform a new impregnation step on another raw wood or on the impregnated wood.

According to one embodiment, the contacting of the raw wood with the impregnating composition comprises (or even consists of) a vaporization of the impregnating composition on the raw wood or an immersion of the raw wood in a composition bath. impregnation.

According to a particular embodiment, the raw wood is immersed in the impregnating composition for a time sufficient to allow impregnation of the wood impregnating composition, then the wood is removed from the composition and incubated for a sufficient period of time to allow the enzyme to act on the wood. Alternatively, the raw wood is immersed in the impregnating composition and is allowed to incubate for a time sufficient to allow the enzyme to act on the wood. The incubation may be implemented in any suitable device known to those skilled in the art, for example in a storage cabinet.

According to a preferred embodiment, the contacting of the raw wood with the impregnating composition is carried out by spraying raw wood chips, compressed from a compression screw directly into a bath of impregnating composition. This allows optimal chip absorption (the chips sucking the composition in the manner of a sponge) and promotes the action of the composition in the heart of the wood fibers.

The contacting of the raw wood with the impregnating composition is preferably carried out for a period ranging from 5 minutes to 240 minutes, from 25 minutes to 180 minutes, from 45 minutes to 120 minutes, more preferably 55 minutes. at 65 min. The impregnating composition is preferably carried out at a temperature ranging from 35 to 80 ° C, from 40 to 70 ° C, more preferably from 45 to 55 ° C. It is preferably carried out at a pH ranging from 3 to 11, from 4 to 7, more preferably from 4.5 to 5.5. Such conditions are advantageous for optimizing the effectiveness of the composition according to the invention.

The impregnation stage can be stopped by steaming (contacting the impregnated wood with steam) or washing with water, in order to stop the activity of the enzyme. The duration of steaming or washing with water is preferably from 1 to 10 minutes, more preferably from 3 to 7 minutes. Preferably, steaming is carried out at atmospheric pressure.

Advantageously, the impregnation step may be repeated several times, in particular two to four times. The various embodiments mentioned above can also be combined with each other. Finally, it should be noted that the impregnating composition can be prepared separately and then brought into contact with the raw wood, as explained above, but it can also be prepared directly in contact with the raw wood. In this case, the various compounds of the impregnating composition are added successively and directly to the raw wood. Optional step of chemical post-treatment

In addition to the impregnation, the wood can be subjected to a complementary treatment, called post-treatment. This post-treatment comprises contacting with a chemical composition comprising an alkaline agent and a reducing agent. This post-treatment is advantageous for softening the lignin and developing the mechanical characteristics of the fibers. In particular, it is advantageous when it is desired to manufacture a chemo-thermomechanical pulp (CTMP).

This step is preferably carried out after the impregnation step to avoid a potential inhibition of the enzymes of the impregnating composition.

It can be implemented before or after the refining step. It is preferably carried out between the impregnation stage and the refining stage, which makes it possible to increase the energy saving of the refining. According to one embodiment, the contacting of the wood with the chemical composition comprises a vaporization of said composition on the wood or immersion of the wood in a bath of said composition.

According to one embodiment, the alkaline agent is selected from sodium hydroxide, magnesium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium silicate, or mixtures thereof. Preferably, the alkaline agent is chosen from sodium silicate, sodium hydroxide or their mixture.

According to one embodiment, the reducing agent is chosen from sodium sulphite Na ₂ S ₂ O ₃ , sodium bisulfite NaHSO ₃ or their mixture.

According to one embodiment, the alkaline agent is present in a content ranging from 0.1% to 20% by weight, preferably from 1% to 10% by weight, relative to the weight of wood.

According to one embodiment, the reducing agent is present in a content ranging from 0.1% to 30% by weight, preferably from 1% to 20% by weight, relative to the weight of wood.

The chemical post-treatment step is preferably carried out at a temperature of from 10 ° C to 150 ° C, in particular from 60 ° C to 120 ° C. It is preferably carried out for a time ranging from 1 minute to 120 minutes, preferably from 1 to 60 minutes.

The chemical post-treatment step may be terminated by any means for stopping the reaction of the chemical agents on the wood, for example by washing with water.

Advantageously, the chemical post-treatment step can be repeated several times, in particular twice to four times, which makes it possible to further reinforce the papermaking capabilities of the fibers.

Refining stage

After the impregnation step (and the optional chemical post-treatment step), mechanical refining of the impregnated wood is carried out so as to obtain a mechanical pulp. Mechanical refining includes a primary mechanical refining (also known as pulping), intended to pulp the wood possibly, followed by at least a secondary mechanical refining, intended to develop the papermaking capabilities of the fibers. Secondary refining is eventually followed by one or more subsequent mechanical refining (tertiary refining, refining of refusals, etc.).

The mechanical refining is preferably carried out under pressure so as to allow a more selective separation of the fibers. Primary refining can be carried out by grinding or grating the wood with the grinding wheel (under water flow) or in a disc refiner.

According to one embodiment, the primary refining of the wood is carried out in a disc refiner. The pressure is preferably adjusted so as to reach a refining temperature of between 105 ° C and 115 ° C. Advantageously, the pressure ranges from 0.5 to 5 bar, preferably from 1 to 3 bar. The rotational speed of the discs is preferably from 1000 to 5000 rpm, preferably from 1000 to 3000 rpm.

According to one embodiment, the secondary refining of the wood is implemented in a disc refiner. The secondary refining is preferably carried out at a pressure of from 0.1 to 5 bar, preferably from 0.5 to 3 bar. The rotational speed of the discs is preferably from 1000 to 5000 rpm, preferably from 1000 to 3000 rpm.

According to one embodiment, the secondary refining is implemented so as to have at its disposal dough rate pasta ranging from 250 to 50 mL CSF (Canadian Standard Freeness).

The refining step (s) subsequent to defibration can comprise several stages. For example, after defibering, the product can be separated into an accepted fraction and a rejected fraction, and the rejected fraction refined before mixing with the accepted fraction. It is possible to provide for such intermediate separations several times.

At the end of the refining, a mechanical paper pulp is obtained which can be in particular:

- A mechanical pulp of shredder (SGW) obtained from logs or refined blocks at atmospheric pressure with grinding wheels;

pressurized mechanical pulp (PGW) pulp obtained from logs or refined pressurized blocks with grinding wheels;

- a mechanical pulp refiner (RMP) obtained from chips or sticks in refiners working at atmospheric pressure;

a thermomechanical (TMP) or thermomechanical high temperature paper pulp (HTMP) obtained from chips or logs in refiners after heat treatment of the wood by steaming with steam at high pressure;

a chemothermomechanical paper pulp (CTMP) obtained by chemical treatment in the presence of a chemical composition comprising an alkaline agent and a reducing agent at a temperature greater than or equal to 100 ° C. and refining under pressure. At the end of the refining, a mechanical paper pulp is obtained, preferably having a degree of whiteness, measured according to ISO 2470, greater than or equal to 50%, preferably greater than or equal to 55%, ideally greater than or equal to at 57%.

The specific energy saving achieved by virtue of the invention is advantageously greater than or equal to 10%, even greater than or equal to 12%, even greater than or equal to 14%, even greater than or equal to 18%, or even greater than or equal to 32%. %, compared to a process for manufacturing a mechanical paper pulp obtained by refining a wood pre-impregnated under the same conditions but with water.

Optional chelation step

The chelation, when implemented, preferably occurs after the impregnation stage (that is to say once the impregnation stage is completed), advantageously after the refining, in order to avoid a possible inhibitory interaction with the enzyme. The chelation comprises contacting the mechanical pulp resulting from the refining with a chelating composition comprising a chelating agent, said chelating composition preferably being an aqueous solution.

The chelating agent may be any chemical compound conventionally used for this purpose in the field. Preferably it is ethylene diamine tetraacetic acid or a sodium salt thereof, or diethylene triamine penta-acetic acid or a sodium salt thereof.

The chelating agent has a particular affinity for trace metal cations in mechanical pulp. The purpose of the chelation treatment is to neutralize these cations by sequestering them and to remove them from the mechanical paper pulp by washing it. The completion of the chelation step contributes to improving the performance of a subsequent bleaching treatment (in particular with hydrogen peroxide).

The amount of chelating agent used in the chelation step is preferably from 0.05% to 3% by weight, preferably from 0.1% to 2% by weight, preferably from 0.2% to 1% by weight. % by weight, in particular from 0.3% to 0.5% by weight, relative to the weight of dry mechanical pulp.

The duration of the chelation step is preferably greater than or equal to about 30 minutes.

The chelation step is carried out at a temperature of preferably 4 ° C to 95 ° C, preferably 25 ° C to 85 ° C, more preferably 35 ° C to 80 ° C. A temperature of about 60 ° C is particularly suitable. The consistency of the mechanical paper stock in the chelation step is preferably 0.5% to 20% by weight of dry mechanical paper stock, preferably 2 to 15% by weight of dry mechanical stock more preferably from 3 to 12% by weight of dry mechanical pulp, relative to the weight of dry mechanical pulp.

Optional step of bleaching

The bleaching preferably occurs after the chelation (or after refining if the chelation is absent), that is to say once the chelation step (or the refining step if the chelation is absent) is completed. .

Bleaching comprises contacting the mechanical paper pulp from the chelation step (or refining if the chelation is absent) with a bleaching composition.

The consistency during the bleaching step is preferably from 1% to 50% by weight of dry mechanical pulp, preferably from 10 to 40% by weight of dry mechanical pulp, more preferably from 20 to 30% by weight. % by weight of dry mechanical pulp, relative to the weight of dry mechanical pulp.

Bleaching has faster reaction kinetics at high consistency (whereas for chelation reaction kinetics are fast even at low consistency). The consistency of the mechanical paper stock can be increased by pressing it, for example, and by eliminating filtrates comprising in particular the chelated metals.

The contacting is preferably by simple mixing of the bleaching composition with the paper pulp. The type of equipment used for mixing is adapted according to the consistency of the pulp: direct mixing by means of an injection pump if the consistency is low or medium (less than 10%); mixer or mixer for a higher consistency (up to about 40%).

The bleaching composition is preferably an aqueous solution. The bleaching composition preferably comprises a bleaching agent and an alkaline agent.

The bleaching agent may be any chemical compound conventionally used for this purpose in the field. Preferably it is hydrogen peroxide or sodium hydrosulfite.

The amount of bleaching agent used is preferably from 0.5% to 10% by weight, preferably from 1% to 8% by weight, preferably from 1.5% to 6% by weight. weight, in particular from 2% to 4% by weight, relative to the weight of dry mechanical pulp.

The alkaline agent may be selected from oxides, hydroxides, silicates and carbonates of alkali metals and alkaline earth metals, ammonia, ammonia and mixtures thereof. Among the basic species preferred for the choice of the alkaline agent, mention may be made of potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, sodium silicate magnesium carbonate and mixtures thereof. Sodium hydroxide, potassium hydroxide or their mixture is particularly preferred. Preferably, the alkaline agent of the bleaching composition comprises sodium silicate. Sodium silicate has an auxiliary stabilizing function of the bleaching agent (especially hydrogen peroxide). It is also possible to provide in the bleaching composition another stabilizing agent in addition to or instead of sodium silicate. Polyhydroxyacrylate compounds are possible stabilizing agents.

The amount of alkaline agent used is preferably from 0.5% to 10% by weight, preferably from 1% to 6% by weight, preferably from 1.4% to 4% by weight, in particular from 1% to 6% to 2.5% by weight, relative to the weight of dry mechanical pulp.

The bleaching composition may also comprise a chelating agent as defined above, especially if the chelation step is absent or has resulted in incomplete chelation.

It should be noted that the bleaching composition can be prepared separately and then brought into contact with the mechanical paper pulp, but it can also be prepared directly in contact with the mechanical pulp. In this second case, the various compounds of the bleaching composition are successively directly added to the mechanical pulp.

The duration of the bleaching step varies depending on the type of agent used.

In the case of hydrogen peroxide, this duration is preferably from 10 minutes to 8 hours, preferably from 30 minutes to 6 hours, more preferably from 2 hours to 4 hours.

The bleaching step is carried out at a temperature of preferably 4 ° C to 95 ° C, preferably 25 ° C to 85 ° C, more preferably 35 ° C to 80 ° C. A temperature of about 70 ° C is particularly suitable.

The bleaching step can be repeated several times, for example twice. At the end of the first bleaching, a mechanical pulp having a degree of whiteness, measured in accordance with ISO 2470-2: 2008, is obtained, greater than or equal to 57%, more preferably greater than or equal to 60 %, ideally greater than or equal to 62% or even greater than or equal to 65%.

Paper manufacturing

Finally, the invention relates to a papermaking process comprising the manufacture of mechanical pulp according to the preceding method and then the use of this mechanical paper pulp to produce paper.

The mechanical paper stock can be dried and shaped into sheets in a conventional paper machine in the field.

The mechanical paper stock may also be fed to a dough press machine to be dried and preformed into sheets. The leaves can be baled for transfer to a paper mill for possible subsequent processing.

Advantageously, the tear resistance of the paper obtained by virtue of the implementation of the present invention (measured according to the standard NF EN 21974 after sheeting the mechanical pulp according to the standard NF EN 5269-1) is increased 3%, or even 9%, or even 11%, in relation to a mechanical pulp obtained by refining a wood pre-impregnated with water.

Measurement settings

The activity of the enzyme laccase is expressed in LAMU / ml. A LAMU unit corresponds to the amount of laccase enzyme which, under given conditions (pH 7.5 and temperature 30 ° C), degrades 1 μιτιοΙ of syringaldazine per minute. This activity is determinable from absorbance measurements by spectrophotometry. Indeed, during the reaction according to which a laccase (EC 1.10.3.2), p-diphenol: dioxygen oxidoreductase, catalyzes the oxidation of syringaldazine (4,4'- [azinobis (methanylylidine)] bis (2,6- dimethoxyphenol)) to the corresponding quinone (4,4 '- [azobis (methanylylidine)] bis (2,6-dimethoxycyclohexa-2,5-dien-1-one), there is a change in absorption by syringaldazine at a wavelength of 530 nm.

For the measurement, we use:

a buffer solution (pH 7.5) at 25 mM Tris / malate (prepared from 25 ml of a 1.0 M aqueous solution of Tris (hydroxymethyl) aminomethane, 5 ml of a 1.0 aqueous solution; M maleic acid, and the sufficient amount of water to obtain IL buffer solution), a 0.28mM syringaldazine solution (prepared by diluting 25 ml of 0.56mM syringaldazine alcoholic solution in the sufficient quantity of water to obtain 50 ml of syringalazine solution, the 0.56mM syringaldazine alcoholic solution being itself obtained by dissolving 10.0 mg of syringaldazine (Sigma S-7896) in the sufficient amount of 96% ethanol to obtain 50 ml of syringaldazine alcoholic solution),

an aqueous solution of ethanol at 6% by weight,

a dilution solution for the enzyme (containing 25.0 g of PEG 6000, 5.0 g of Triton X-100 and a sufficient quantity of water to obtain 0.5 L of solution). The laccase samples to be tested are diluted F factor with this solution to approach an activity of 0.18 LAMU / mL.

Absorbance measurements are made with the spectrophotometer at a working temperature of 30 ° C. A vial is prepared with 1 ml of buffer solution, 25 μl of diluted laccase, and 75 μl of 0.28 mM syringaldazine solution is added. The mixture is briefly mixed and the acquisition of the absorbance measurement of a radiation of wavelength 530 nm is started immediately.

The activity is calculated according to the formula:

Activity (LAMU / mL) = AA ₅₃₀ nm x 0.677 x F

with AA ₅₃₀ nm the absorbance difference at 530nm measured over the period 60-90 seconds and F the dilution factor of the enzyme.

The "Canadian Standard Freeness" (CSF) dewatering index is measured according to the international standard ISO 5267-2. It reflects the ease with which water can be extracted from a mechanical pulp. The smaller the index, the more mechanical pulp drains poorly. This parameter is an indicator of the degree of refining achieved during mechanical refining of the pulp.

The whiteness of the mechanical paper stock is determined by measuring its diffuse blue reflectance factor as defined in ISO 2470-2: 2008.

For an X test, the whiteness gain corresponds to the difference between whiteness measured at the end of QP whitening and the whiteness measured at the end of refining.

The total specific energy of refining is obtained by summing up the values of the electrical consumptions measured for each of the stages preceding the refining and until its exit (for example compression of wood chips, defibration and secondary refining).

For an X test, the realized energy saving corresponds to the difference between the specific refining energy of a reference test, carried out in the same conditions that the test X with the difference that it implements an abiotic impregnation composition, and the specific energy refining of the test X.

In order to evaluate the resistance of the fibers in the manufactured mechanical paper pulp, the latter is put into sheets in accordance with standard NF EN 5269-1 and the tear resistance of the sheets is measured according to standard NF EN 21974.

EXAMPLES

The following examples illustrate the invention without limiting it.

The raw materials used are as follows:

- fresh Norwegian spruce chips supplied by HOLMEN,

- chips from fresh poplar logs supplied by a logging operation in the Lyon region,

- fresh eucalyptus chips from Spain supplied by ENCE,

laccases Myœliophthora sold by NOVOZYMES under the reference NS51003, having an activity of 1000 LAMU / mL measured according to the protocol indicated above,

diethylhydroxylamine (DEHA) marketed by the company Arkema,

4-Hydroxy-3,5-dimethoxybenzaldehyde (Syringaldehyde),

- diethylene triamine pentaacetic acid (DTPA),

- hydrogen peroxide,

- sodium silicate,

- sodium hydroxide,

- magnesium sulfate.

Table 1: Impregnation Composition

For each test, an impregnating composition is prepared according to Table 1 (the percentages are given by weight relative to the total weight of the composition). For this, the water is heated to 50 ° C, the pH is adjusted to 5 by addition of sulfuric acid, the commercial solution of laccase and lastly the DEHA (or syringaldehyde as appropriate). The impregnating compositions of tests 1, 6 and 9 are abiotic reference compositions. The compositions of tests 2, 4 and 5 are comparative. The compositions in accordance with the invention are those of tests 3, 7, 8, 10 and 11.

The effective absorption capacity of dry chips is 1.04 L of impregnating composition per kilogram of dry wood chips. For each test, the excess composition is used, at a rate of 70L per 10 kg of dry wood chips.

Tests 1 to 5: thermomechanical pulping (TMP) and bleaching

Spruce chips are steamed at atmospheric pressure for 15 minutes and then introduced into a compression screw (ANDRITZ AG Modular Screw Device Impressafiner ™ 6 inch), connected to a vat containing the impregnating composition. At the outlet of the screw, the compressed chips are directly expelled into the impregnating composition, where they are allowed to incubate for 1 hour. The impregnating composition is extracted and then the chips are subjected to steam steaming for 5 minutes to stop the enzymatic activity.

The chips thus pre-treated are transferred into a mechanical pulping pilot (disc refiner) to be mechanically defibrated and then refined. Defibering (primary refining) is carried out at a pressure of 2 bar and disc rotation at 3000 rpm. Secondary refining is carried out at a pressure of 1 bar. The gap between the discs is gradually adjusted so as to obtain five mechanical paper pulps of freeness ranging from 250 mL to 50 mL CSF. The whiteness of the five mechanical paper stocks is measured according to ISO 2470-2: 2008.

After refining, each obtained TMP mechanical pulp is bleached in a two-step process comprising a chelation step (Q) followed by hydrogen peroxide bleaching (P). In step Q, the consistency of the mechanical paper stock is adjusted to 10% by weight. Step Q includes putting in contact at a temperature of 60 ° C for 30 minutes, this mechanical paper pulp with 0.4% by weight of diethylene triamine penta acetic acid (DTPA) relative to the total weight of dry mechanical pulp. In step P, the consistency of the mechanical pulp obtained at the end of step Q is adjusted to 25% by weight. Step P comprises contacting, at a temperature of 70 ° C for 120 minutes, this mechanical paper stock with a bleaching composition comprising 3% hydrogen peroxide, 1.9% sodium hydroxide and 2% sodium silicate in percentages by weight relative to the total weight of dry mechanical pulp. The whiteness of the five mechanical paper stocks is measured according to ISO 2470-2: 2008.

The mechanical paper stocks are then put into sheets in accordance with standard NF EN 5269-1. The tear resistance of the sheets is measured according to standard NF EN 21974.

The specific energy consumption is calculated as described above, namely by summing up the energy consumption of each step of the mechanical pulping process until the end of the refining: 1 ^st steaming, compression / expulsion, 2 ^nd parboiling, defibration and subsequent refining.

The results are reported in Table 2 below after interpolation of the values at 100 mL CSF.

As regards the specific energy consumption of refining, test 3 according to the invention shows that: the invention allows a significant reduction in the specific energy consumption of refining;

the combination of laccase and DEHA allows a greater reduction in the refining specific energy consumption than the compounds taken separately (tests 4 and 5);

- in combination with laccase, DEHA allows a reduction in the refining specific energy consumption greater than syringaldehyde (test 2).

As regards the whiteness of the mechanical pulp, the test 3 according to the invention shows that:

the invention makes it possible to significantly increase the degree of whiteness of the manufactured mechanical pulp (test 1);

the combination of laccase and DEHA makes it possible to increase the degree of whiteness of the paper pulp, unlike the compounds taken separately (tests 4 and 5 versus test 1);

in combination with laccase, DEHA further increases the degree of whiteness of the pulp than syringaldehyde (test 2).

With regard to the tear strength of the paper, the test 3 shows that the invention preserves the paper qualities of the fibers.

Tests 6 to 8: Influence of the content of compounds in the impregnating composition

These additional tests are carried out in order to determine the influence of the quantity of reagents used in the impregnating composition according to the invention. The impregnating composition used for each test is given in Table 1. The impregnating composition of Test 6 corresponds to an abiotic reference composition. The compositions of tests 7 and 8 are in accordance with the invention. The same procedure is used in tests 1 to 4. The results are reported in table 3 below.

Table 3

Test 7 (compared with test 6) shows that, even when the amounts of laccase and DEHA are decreased, the impregnating composition according to the invention makes it possible to reduce the specific energy consumption of refining, to increase the degree of whiteness of the manufactured mechanical pulp and to preserve the strength of the paper which is derived therefrom.

Test 8 (compared to tests 6 and 7) shows that below a certain mediator content, the impregnating composition no longer makes it possible to reduce the specific energy consumption of the refining operation but nevertheless makes it possible to increase the degree of whiteness of the manufactured mechanical pulp and to preserve the strength of the paper which is derived therefrom.

Tests 9 to 11: chemical-thermomechanical pulping (CTMP ^' ) and bleaching

Poplar wood chips are pulped according to the steaming, pressing and impregnation stages identical to those of tests 1 to 4. The impregnation composition used for each of the tests is indicated in the table. In particular, the impregnating composition of test 9 corresponds to an abiotic composition which serves as a reference. The compositions of tests 10 and 11 are in accordance with the invention.

A second chip treatment is carried out by adding to the vat 2% by weight of sodium sulfite and 1% by weight of sodium hydroxide, relative to the total weight of dry chips. The temperature of the medium is brought to 125 ° C. and the chips are left to impregnate for 15 minutes.

The impregnated chips are subjected to defibration at a pressure of 2 bar and rotation of disks at 3000 revolutions per minute, then to a second mechanical refining at atmospheric pressure. The gap between the discs is gradually adjusted so as to obtain five mechanical paper pulps of freeness ranging from 400 to 100 mL CSF. The whiteness of the five mechanical paper stocks is determined according to ISO 2470-2: 2008.

After the refining, each CTMP mechanical pulp obtained is bleached comprising three steps: a chelation step (Q) followed by two successive treatments with hydrogen peroxide (PP). In step Q, the consistency of the mechanical paper stock is adjusted to 10% by weight. Step Q comprises contacting, at a temperature of 60 ° C for 30 minutes, this mechanical paper pulp with 0.4% by weight of diethylene triamine pentaacetic acid (DTPA) relative to the total weight of dough dry mechanical paper.

In the first step P (PI), the consistency of the mechanical pulp obtained at the end of step Q is adjusted to 14% by weight. Step PI comprises contacting, at a temperature of 70 ° C for 120 minutes, this mechanical paper stock with a bleaching composition comprising 2.2% hydrogen peroxide, 1.5% hydroxide of sodium, 1% of sodium silicate, 0.075% of magnesium sulphate, in percentages by weight relative to the total weight of dry mechanical pulp. The whiteness of the five mechanical paper stocks is determined according to ISO 2470-2: 2008.

In the second step P (P2), the consistency of the mechanical pulp obtained at the end of step PI is adjusted to 20% by weight. Step P2 comprises contacting, at a temperature of 70 ° C. for 120 minutes, this mechanical paper pulp with a bleaching composition comprising 3.4% hydrogen peroxide, 1.7% sodium hydroxide. , 1.6% sodium silicate, 0.075% magnesium sulphate, in percentages by weight relative to the total weight of dry mechanical pulp. The whiteness of the five mechanical paper stocks is determined according to ISO 2470-2: 2008.

The specific energy consumption of the process is calculated for each mechanical pulp as described above.

The results are reported in Table 4 below after interpolation of the values to 300 mL CSF.

Table 4

Regarding the specific energy consumption:

the tests 10 and 11 (compared with the test 9), especially the test 10, show that the use of an impregnating composition according to the invention during the refining allows a significant reduction in the specific energy consumption. refining the CTMP process;

Concerning the whiteness of mechanical pulp:

the tests 10 and 11 (compared with the test 9) show that the use of an impregnating composition according to the invention during the refining makes it possible to obtain a whiter CTMP mechanical paper pulp at the same time. the result of refining only after a subsequent bleaching thereof;

the invention increases the degree of whiteness of the mechanical pulp obtained after the first bleaching carried out after refining.

Claims

A method of manufacturing mechanical pulp comprising at least:

in which R 1 and R 2 are identical or different groups, chosen from a hydrogen atom, a linear or branched, saturated or unsaturated hydrocarbon-based chain containing from 1 to 14 carbon atoms, each hydrocarbon-based chain possibly being substituted with one or a plurality of functional groups selected from -OH, -SO 3, benzyl, amino, mercapto, keto, carboxyl, where R 1 and R 2 may together form a ring structure, to obtain an impregnated wood; and a step of mechanical refining of the impregnated wood, so as to obtain a mechanical pulp.

Process according to the preceding claim, in which R1 and R2 are identical or different groups chosen from a hydrogen atom or a C1-C8 alkyl chain and preferably identical or different C1-C4 alkyl chains.

Method according to one of the preceding claims, wherein the mediator is diethyl hydroxylamine (DEHA).

Process according to any one of the preceding claims, in which the impregnating composition is used to manufacture and relative to its total weight: From 0.01% to 10% by weight of a 1000 LAMU / ml solution of laccase of said solution, and

0.1% to 10% by weight of mediator.

Process according to any one of the preceding claims, in which the impregnating composition is used at a rate of 0.1 to 12 L / kg of the raw wood to be impregnated, preferably at a rate of 1 to 10 L / kg of the raw wood to impregnate.

Process according to any one of the preceding claims, in which the raw wood is chosen from softwoods, hardwoods or their mixtures, preferably from a spruce wood, a poplar wood, a eucalyptus wood or their mixture.

A method as claimed in any one of the preceding claims wherein the raw wood is in the form of chips.

A process according to any one of the preceding claims, wherein the contacting during the impregnation step is carried out for a period of from 5 minutes to 240 minutes, preferably from 25 minutes to 180 minutes, preferably from 45 min at 120 min, more preferably 55 min at 65 min.

A process according to any one of the preceding claims, wherein the impregnating step is carried out at a temperature of from 35 ° C to 80 ° C, more preferably from 40 ° C to 70 ° C, more preferably from 45 ° C to 55 ° C.

Process according to any one of the preceding claims, in which the impregnation stage is carried out at a pH ranging from 3 to 11, in particular from 4 to 7, even more preferably from 4.5 to 5, 5.

Process according to any one of the preceding claims, comprising, before the impregnation step, steam steaming of the raw wood, preferably carried out for 5 min to 30 min, more preferably 10 min to 20 min. Process according to any one of the preceding claims, comprising, prior to the impregnation step, pressing of the raw wood, preferably carried out after steaming of the raw wood.

Process according to any one of the preceding claims, comprising, at the end of the impregnation step, steam steaming of the impregnated wood, preferably carried out for 1 min to 10 min, preferably from 3 min to 7 min.

A method as claimed in any one of the preceding claims comprising, after the refining step, a bleaching step, comprising contacting the mechanical pulp with a bleaching composition.

Process according to the preceding claim, in which the bleaching composition comprises a bleaching agent and at least one alkaline agent chosen from: oxides, hydroxides, silicates and carbonates of alkaline-earth metals and alkaline metals, ammonia , ammonia and mixtures thereof, more preferably selected from potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, sodium silicate, sodium carbonate, sodium carbonate, magnesium and mixtures thereof, even more preferably selected from sodium hydroxide, magnesium hydroxide and mixtures thereof.

Method according to the preceding claim, wherein during the bleaching step, use is made of:

from 0.5% to 10% by weight, preferably from 1% to 8% by weight, more particularly preferably from 1.5% to 6% by weight of bleaching agent, relative to the total weight of dough mechanical paper;

from 0.5% to 10% by weight, preferably from 1% to 6% by weight of alkaline agent, relative to the total weight of mechanical paper stock.

A process according to any one of the preceding claims comprising a chelation step, preferably between the step of refining and a step of bleaching the mechanical paper pulp, comprising contacting the mechanical pulp with a chelating composition comprising a chelating agent, preferably selected from ethylene diamine tetra-acetic acid, its sodium, diethylene triamine penta-acetic acid and its sodium salts.

A method as claimed in any one of the preceding claims, wherein the mechanical paper stock is a mechanical paper stock SGW, PGW, RMP, TMP, HTMP or CTMP, preferably a TMP or CTMP mechanical paper stock.

A method of manufacturing a mechanical paper stock, comprising, in order, the following steps:

- optionally a steaming of raw wood,

- possibly a pressing of a raw wood,

at least one step of impregnating a raw wood with an impregnating composition as defined in any one of Claims 1 to 5, to obtain an impregnated wood,

- optionally steam steaming of the impregnated wood,

optionally a step of chelating the mechanical pulp,

possibly a bleaching of the mechanical paper stock.

Impregnation composition of a raw wood as defined in any one of claims 1 to 5.

21. Use of an impregnating composition as defined in any one of claims 1 to 5 in a process for manufacturing mechanical pulp to lower the energy consumption of said process.

22. Use of an impregnating composition as defined in any one of claims 1 to 5 in a method of manufacturing mechanical pulp to increase the whiteness of said pulp.

Use of an impregnating composition as defined in any one of claims 1 to 5 in a mechanical pulp manufacturing process comprising a mechanical refining step, said impregnating composition being used before the step of mechanical refining.

A papermaking process, comprising making a mechanical paper stock according to any one of claims 1 to 19, and using said mechanical paper stock to produce paper.