Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/06—Vegetable or imitation parchment; Glassine paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/005—Microorganisms or enzymes

Definitions

• the present invention relates to a method of manufacturing a tracing paper from a cellulosic fiber composition including a step of enzymatic treatment of fibers.
• tracing paper is used traditionally in the paper industry to refer to a so-called “natural” tracing paper obtained from an aqueous suspension of paper pulp which has undergone extensive refining of cellulose fibers which 'it contains.
• paper pulps must undergo a refining step in order to hydrate and fibrillate the fibers.
• This step densifies the fibrous mat forming on the web of the paper machine and controls the physical and optical characteristics of the paper sheet.
• this refining step is pushed to obtain a very dense sheet almost free of air (voids), which gives transparency to the paper.
• the mechanical refining of a paste in aqueous suspension is then carried out before it is used on the paper machine.
• This fibrillation step is carried out in mechanical refiners which are large energy consuming devices.
• the high degree of refining of the fibers causes machinability problems, in particular problems of drainability of the dough during the formation of the sheet on the paper machine.
• machinability problems in particular problems of drainability of the dough during the formation of the sheet on the paper machine.
• the dewatering of paper pulp on the web of a paper machine plays a particularly important role in productivity, especially for tracing paper. Indeed, it is necessary to heat the refined pulp at temperatures of 80 to 95 0 C for example to facilitate drainage and thus increase the productivity of the paper machine. This also leads to some energy consumption.
• French patent application FR 2 557 894 describes a process for treating paper pulps with a particular enzymatic solution based on xylanases promoting fibrillation. According to this treatment method, a solution of xylanases is added to a fibrous suspension of paper pulp. The dough thus treated is then refined mechanically. This enzymatic treatment of the pulp causes a loosening of the fiber structure, loosening which favors the subsequent action of the refining step.
• European Patent Application EP 0 262 040 discloses a process for treating a paper pulp based on recycled fibers with an enzyme preparation containing cellulases and / or hemicellulases.
• the purpose of this document is to improve the drainage of the aqueous suspension of fibrous material without any undesirable effect on the mechanical characteristics of the paper made from this paste.
• the technique used to improve the dewatering of the aqueous fiber suspension fed to the web of a paper machine does not make use of a virgin fiber paper pulp having low fibrillation and fine rates.
• this document does not describe the manufacture of a tracing paper.
• the present invention aims to solve the disadvantages of the prior art of the manufacture of a tracing paper, in particular to reduce the energy costs of this manufacture while maintaining good mechanical and optical characteristics of the tracing paper.
• the invention thus provides a method for manufacturing a sheet of tracing paper having good mechanical characteristics and a low opacity index, the pulp of which is based on virgin cellulosic fibers in aqueous suspension is subjected to the action of an enzyme preparation based on cellulases prior to mechanical refining.
• the process according to the invention makes it possible, on the one hand, to improve the dewatering of the suspension paste by accelerating the dewatering, and / or to reduce the temperature of the suspension pulp in headbox that will be drained, and secondly to have a gain in energy during the production of tracing paper, in particular by reducing the amount of refining energy required.
• the method of manufacturing a sheet of tracing paper having an opacity index of less than 40%, measured according to ISO 2469, according to the invention is characterized in that it comprises the following steps: a) acting on an aqueous suspension of pulp whose fibrous composition comprises at least 50% by dry weight of virgin cellulosic fibers, an enzymatic preparation containing cellulases; b) after an enzymatic action time on said pulp of not more than 60 minutes (in step a)), the enzymatic action of the cellulases on said paper pulp is inhibited; c) the pulp is mechanically refined; paper mill obtained in step b), d) said fine paper pulp is drained onto the fabric of the paper machine, e) the sheet thus formed is dried so as to obtain said sheet of tracing paper.
• a tracing paper is manufactured which can have an opacity index of less than 30%, measured according to the ISO 2469 standard.
• the fibrous composition of the paper pulp according to the invention may comprise at least 50% of virgin cellulosic fibers in dry weight, preferably at least 70% of virgin cellulosic fibers in dry weight, relative to the total dry weight of the fibrous composition. pulp. More preferably still the composition may comprise 100% virgin fibers.
• non-recycled fibers these fibers may in addition come from broken manufacturing.
• Broken manufacturing is paper removed at any stage of manufacture on the paper machine and generally pulped.
• wet manufacturing breaks that is to say accumulated in the wet part of the paper machine
• dry manufacturing breaks accumulated at any point of the dryness of the machine. paper machine, trimmings from winding, re-slitting and cutting operations as well as paper rejected in sorting.
• papermaking pulps used for the manufacture of tracing paper are selected from bleached northern softwood kraft pulp, bleached softwood kraft pulp from the South and blend thereof. These papermaking pulps may possibly be associated with small quantities of hardwood type pulp. Bleached sulphite pulps can also be used for the manufacture of tracing paper.
• step a) The enzymatic action in step a) is performed on the pulp at the required pH and temperature conditions for the enzymes to be active, according to the knowledge in the field of biotechnology.
• the enzymatic preparation of the invention utilizes endo-1,4- ⁇ -glucanase cellulases, which are commonly referred to as "endoglucanases”.
• the pulp is added to the paper pulp composed of at least 50% of virgin cellulosic fibers in aqueous suspension at a rate of 50 g / l, the enzyme preparation containing the cellulases.
• 0.05 to 1 gram of a cellulase, in particular of endoglucanase type is added to said aqueous suspension based on virgin cellulosic fibers per kilogram of paper pulp on a dry weight basis, and the whole is mixed for a time not exceeding 60 minutes.
• the Applicant has found that the enzymatic treatment of the paper pulp in suspension of step a) of the process does not need to be continued beyond 60 minutes.
• the enzymatic reaction of the cellulases is therefore stopped, preferably by inhibiting it by addition of a chemical inhibitor to the pulp suspension.
• the enzymatic action of the cellulases is inhibited by adding to said aqueous suspension of paste a chemical inhibitor so that the enzymatic treatment time of said aqueous suspension of dough does not exceed 60 minutes.
• said chemical inhibitor is a strong oxidizer.
• said chemical inhibitor is chosen from sodium hypochlorite and hydrogen peroxide, especially used in the form of an aqueous solution.
• the enzymatic action time of the cellulases on the aqueous pulp suspension is preferably between 5 and 45 minutes, more preferably between 5 and 30 minutes.
• One method to determine that enzyme inhibition has occurred is to track the viscosity of CMC (carboxymethylcellulose) solutions made with the water of dough samples taken before and after the addition of the inhibitor, according to the method described later after the examples.
• CMC carboxymethylcellulose
• This method makes it possible to optimize the concentration and quantity of the inhibitor as well as the inhibition time.
• the pulp thus treated, resulting from step b) of the process is subjected according to step c) of the process of the invention to a mechanical refining.
• the mechanical refining is carried out by means of refiner (s).
• the paper pulp is refined to a Schopper-Riegler degree greater than 80.
• step d) of the process of the invention the aqueous pulp suspension obtained is deposited on the fabric of a paper machine, generally a flat-bed paper machine, and the water is drained by gravity and by means of foils and other dewatering devices.
• Step d) of the tracing paper manufacturing method according to the invention is characterized by an improvement in the drip rate of the dough on the fabric of the paper machine compared to the same dough not treated with enzymes.
• Speed dewatering of the aqueous suspension of paste obtained at the end of step c) of the process is characterized by a dewatering time determined according to the test described below in the paragraph "DESCRIPTION AND CONDITIONS OF REALIZATION OF THE MEASUREMENT OF "DRAINAGE” for a given volume, between 40 and 60 seconds.
• An improvement in the drip speed of the dough on the web of the paper machine during step d) of the method according to the invention was observed for a tracing paper having a given opacity index and less than 40 %.
• the dewatering speed of said processed and refined pulp which is characterized by a dewatering time determined according to the test described below in the paragraph "DESCRIPTION AND CONDITIONS OF REALIZATION OF THE SEWING MEASUREMENT” for a given volume, can be improved by at least 10% with respect to the dewatering speed of a paste that has not been previously treated enzymatically, but refined so as to obtain a tracing paper of opacity value identical, said dewatering speed being characterized by a dewatering time determined according to the same test described below in the paragraph "DESCRIPTION AND CONDITIONS OF REALIZATION OF THE MEASUREMENT OF DRAINAGE".
• the temperature of the suspension of the dough is adjusted between about 80 and 95 ° C to allow better drainage of the paper sheet.
• the inventors have surprisingly found, during their many experiments, that not only the drip rate of the dough on the fabric of the paper machine was significantly improved but also that the temperature of the dough suspension could be reduced by a few degrees Celsius, namely from 2 to 10 0 C for dripping.
• the temperature of the dough in suspension can be adjusted to a temperature of less than or equal to 80 ° C., preferably between 70 ° and 75 ° C., and the dripping speed on the fabric of the paper machine of the dough resulting from step d) remains significantly improved.
• This decrease in the temperature of the pulp suspension as well as the reduction of the pulp refining energy represents an energy gain.
• the refined paste obtained at the end of step c) is heated to said temperature, in the short circuit of the paper machine leading to the headbox of the machine paper. Then, during step e) of the process of the invention, the sheet of tracing paper obtained in step d) of the process is dried on drying rollers.
• the sheet of tracing paper thus obtained has a relatively low opacity index specific to the tracing paper sheets, more specifically an opacity index of less than 40%, preferably less than 30%, measured according to the ISO 2469 standard.
• a dye may be added, for example, in the aqueous suspension of the dough before the head box of the paper machine, so as to obtain a colored sheet of tracing paper.
• 0.2 gram of endo-1,4- ⁇ -glucanase cellulase enzymes per kilogram of the dough mixture on a dry weight basis is added to said aqueous fiber dispersion.
• the enzymatic activity is maintained for 15 minutes and then stopped by adding an aqueous solution of sodium hypochlorite to said aqueous slurry.
• the fiber suspension is at a temperature of about 50 0 C and its pH was adjusted between 6 and 8 to be in the activation conditions of the enzymes.
• the pulp suspension is refined in a mechanical refiner by applying a refining energy of 500 kWh / ton so as to obtain a level of fibrillation leading to a final opacity of the paper sheet of 36%.
• a refining energy 500 kWh / ton so as to obtain a level of fibrillation leading to a final opacity of the paper sheet of 36%.
• refined pulp is heated in short circulation of the paper machine at a temperature of about 80 0 C, and is fed to the headbox and depositing the paste on the wire of a machine flat-table paper, it is drained and pressed. Then, the sheet of tracing paper thus obtained is dried on drying rollers at approximately 100 ° C.
• This pulp suspension is refined in a mechanical refiner by applying a refining energy of 800 kWh / ton so as to obtain a level of fibrillation leading to a final opacity of the paper sheet of 36%.
• the dough thus refined is heated in the short circuit of the paper machine at a temperature of about 85 ° C., and it is brought to the headbox and then deposited on the fabric of a machine. flat-table paper, it is drained and pressed. Then, the sheet of tracing paper thus obtained is dried on drying rollers at approximately 100 ° C. This gives a sheet of tracing paper having an opacity index of 36% and a basis weight of 110 g / m 2 .
• FIG. 1 represents the curve of the opacity index as a function of the refining energy of a sheet of tracing paper resulting from an enzyme-treated paste according to the invention (example 1) and that of a sheet of tracing paper resulting from an untreated paste according to the prior art (example 2).
• FIG. 2 represents the curve of the dewatering time (denoted Dv) as a function of the refining energy of a sheet of tracing paper resulting from an enzyme-treated paste according to the invention (example 1) and that of a sheet of tracing paper obtained from an untreated dough by enzyme according to the prior art (example 2). Results interpretation
• Figure 1 shows the influence of enzymatic treatment on the refining energy of the pulp in aqueous suspension.
• the opacity index of 36% of a sheet of tracing paper obtained according to the same process as that of the invention but whose paste in aqueous suspension is free from any enzymatic treatment. (Example 2), requires a refining energy of 800 kWh / ton while the same opacity index of 36% can be obtained for a sheet of tracing paper as described in Example 1, the pulp in aqueous suspension has was subjected to enzymatic treatment at the rate of 0.2 gram of an endo-l, 4- ⁇ -glucanase cellulase per kilogram of pulp with a refining energy of the order of 500 kWh / ton. Therefore, a tracing paper obtained according to the method of the invention allows a reduction in the energy consumption of refining of about 38%.
• Figure 2 shows the influence of enzymatic treatment on the dewatering time (Dv).
• the tracing paper manufacturing method according to the invention makes it possible to improve the dripping speed of the dough on the fabric of the paper machine, the dripping speed of the dough which is characterized by a time of dyeing. determined according to the test described below in the paragraph "DESCRIPTION
• the dewatering time (in seconds) determined according to the test described below, of a sheet of tracing paper as described in Example 1 according to the invention the paste in aqueous suspension was subjected to enzymatic treatment at a rate of 0.2 gram of an endo-l, 4- ⁇ -glucanase-type cellulase by kilogram of pulp for a refining energy (in kWh / ton) of 500 kWh / ton, is 48 s.
• a sheet of tracing paper obtained according to the same process as that of the invention but whose pulp in aqueous suspension is free of any enzymatic treatment according to Example 2 for a refining energy of 800 kWh / ton is 95 s. Therefore a tracing paper obtained according to the method of the invention allows a marked improvement in the dripping speed of the dough on the fabric of the paper machine, by about 50%, in addition to the gain in refining energy. about 38%, for an opacity equivalent of 36%.
• the measurement of the drip rate of the dough is characterized by the determination of the water flow time by gravitation in seconds for a given volume, this dewatering time of the dough is determined as follows: withdraws a sample of pulp in aqueous suspension and determines its concentration in g / 1, then is prepared from this sample, a liter of aqueous suspension of pulp concentration equal to 0.5 g / l, and its temperature is from 15 ° C.
• the Schöpper-Riegler apparatus standardized according to the international standard ISO5267-1: 1999, is closed and the (two) dripping outlets of the apparatus are put in a standard container according to the same standard, then the liter of the preparation of aqueous paste suspension at 0.5 g / l in the bowl of the Schöpper-Riegler, - the drip outlets of the apparatus are opened and a stopwatch is started simultaneously, the stopwatch as soon as the volume of water Drained in the standardized container reaches 610ml, we note the dewatering time, expressed in seconds, necessary to reach the volume of 610ml of drained water.
• the g / l concentration of the dough is typically determined by filtration of a given volume of the sample of the dough suspension, the recovered dough is dried and weighed. DESCRIPTION OF THE DETERMINATION OF INHIBITION OF ENZYMES:
• Sample A contains the enzymes before inhibition and Sample B (taken at the same place 5 minutes later) contains the enzymes and the inhibitor. Both dough samples are dewatered to recover their respective waters which are then chilled to deactivate any uninhibited enzyme in both batches.
• CMC carboxymethylcellulose
• CMC solution A without inhibitor (once brought to the enzyme activity temperature), rapidly loses its viscosity by the action of enzymes on the cellulose chains whereas CMC solution B, with inhibitor, remains stable in viscosity. We can therefore conclude that the inhibition has taken place.

Landscapes

• Paper (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (2)

Family

ID=38529473

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (3)

Citations (7)

Family Cites Families (1)

• 2006
  • 2006-12-22 FR FR0611303A patent/FR2910500B1/fr not_active Expired - Fee Related
• 2007
  • 2007-12-20 WO PCT/FR2007/052586 patent/WO2008087337A2/fr active Application Filing
  • 2007-12-20 ES ES07871997T patent/ES2719628T3/es active Active
  • 2007-12-20 EP EP07871997.8A patent/EP2122053B1/fr active Active

Patent Citations (7)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events