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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/06—Paper forming aids
• • 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
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/40—Agents facilitating proof of genuineness or preventing fraudulent alteration, e.g. for security paper

Definitions

• the present invention relates to a wrinkle and crease resistant security sheet, its manufacturing method and a security document comprising the sheet.
• resistant to wrinkling and marked crease means that the sheet hardly undergoes the impact of a wrinkle and crease marked thanks to a controlled stiffening of the cellulosic substrate.
• a disadvantage of the used paper supports is that they resist bad wrinkling and wrinkles. Thus, crumpled or folded areas have marked folds, irreversible, poor resistance to soiling, so that these wrinkled areas are weakened and often give rise to tears.
• the mass treatment of paper is one of the solutions that can be considered to improve the resistance to wrinkling.
• the use of flocculation, before the formation of the sheet makes it possible to form a global fiber-flocculating agent-polymer network via the formation of bonds made possible by the presence of the flocculation agent.
• the flocculation of the polymer takes place directly on the fibers thanks to the presence of the flocculation agent. There is therefore no prior formation of polymer flocculates before contacting the fibers.
• the document WO 2008/152299 discloses safety sheets comprising an anionic polymer having a glass transition temperature above -40 ° C and a cationic flocculation agent having good wrinkling resistance.
• WO 2014/083527 discloses safety sheets comprising a polyurethane having an elongation at break greater than 600%, and a cationic flocculating agent, having good wrinkling resistance as well as good mechanical properties such as tensile strength, including breaking lengths dry and wet, resistance to double-fold or tearing.
• EP 1 466 755 and EP 1 466 756 describe safety sheets whose rigidity is increased on the corners with specific watermarks. However, these processes are not economically very attractive and more importantly, they do not allow to treat the entire cellulosic substrate.
• adding stiffness, for example at least 20%, to the safety sheets would further reduce the mechanical impact of the traffic. (wrinkles, creases ...) on the paper.
• the reduction of the physicochemical impact of the circulation such as soiling, wrinkling or folding marked on the paper, it would reduce the rejection by automatic sorting machines.
• the wrinkling, the marked bending and the soiling of a banknote paper lead to a decrease in its rigidity as well as a large number of rejects in automatic sorting machines.
• an anionic dispersion of at least one polymer having a glass transition temperature greater than 23 ° C. is combined with an effective amount of an agent. cationic flocculation during the manufacture of a security sheet.
• anionic dispersion is meant an aqueous suspension of particles having an anionic surface charge.
• Said surface charge is either intrinsically present in the polymer or is provided by a surfactant compound (or surfactant) used in the formation of said particles.
• the polymer according to the present invention may be anionic or not.
• said surface charge is provided by a surfactant compound (or surfactant) used in the formation of said particles.
• dispersion is here used generically and can therefore also refer to an emulsion.
• Polymer aggregates (s) denotes the flocs formed by bringing into contact with the anionic polymer dispersion (s) with the fibers and the flocculation agent. Flocculation of the anionic dispersion of polymer (s) thus occurs as soon as the anionic dispersion of polymer (s) is mixed with the fibers and the flocculation agent.
• the aggregates are thus preserved within this mixture which is then subjected to the successive common steps of the papermaking process, namely dewatering, pressing and drying. Under the effect of said routine steps of the papermaking process and especially by the disappearance of water, said polymer aggregates (s) are thus dispersed within the network formed by the fibers and the flocculation agent.
• said sheet further comprises an auxiliary cationic flocculating agent, said secondary agent, in an amount of between 0.1% and 0.5% by dry weight relative to the total dry weight of fibers and polymer (s).
• This embodiment is particularly advantageous when the proportion of polymer (s) by dry weight relative to the total weight of the fibers in dry is high, in particular when it exceeds 20% by dry weight relative to the total weight of the fibers, because the presence of the secondary cationic flocculating agent makes it possible to perfect the flocculation of the polymer (s).
• the Applicant has found, as illustrated in the examples below, that the presence of aggregates of polymer (s) having a glass transition temperature greater than 23 ° C and flocculation agent (s) in the composition of the sheet according to the invention significantly improved its rigidity on the entire cellulosic substrate and the resistance to soiling while maintaining good resistance to traction, especially the breaking lengths, dry and wet, wet state and double-fold, and good resistance to creasing and tearing of said sheet.
• the phenomenon of flocculation is chemically reflected by the formation in aqueous medium of electrostatic bonds between a chemical compound having ionized groups, namely in the context of the invention the anionic dispersion of polymer (s) having a glass transition temperature greater than 23 ° C, and an agent of flocculation having ionized groups of charge opposite to that of the chemical compound.
• the flocculation agent forms weak atomic bonds (of the order of 5 kJ / mol) with the chemical compound according to a chemical interaction process taking place under mild conditions (for example, at room temperature) and obligatorily in medium solvated (eg water).
• the anionic dispersion of polymer (s) is introduced last, after having introduced the fibers and the flocculation agent.
• the flocculation results in an inhomogeneous distribution of aggregates of polymers (s) intertwined in the network formed by the fibers and the flocculation agent.
• the flocculation system is used for a mass treatment (by volume) of the sheet and is thus carried out in wet part (period during which the fibers are dispersed in water, then forming a fibrous suspension), before the formation of leaf.
• the aggregates of particles are distributed in the interstices left vacant between the fibers during the formation of the sheet. These interstices are no longer accessible after draining, pressing and drying of the sheet as filled by said aggregates.
• said aggregates preferably have hydrophobic and / or oleophobic properties, so that the penetration of the soil is less and the sheet thus has a better resistance to soiling.
• the sheet according to the invention Before the formation of the sheet according to the invention, there is, in addition to the bonds between the anionic particles of the polymer and the cationic charges of the flocculation agent, formation of bonds between the anionic charges of the cellulose and the cationic charges. flocculation agent. It thus forms a global network (fibers - agent flocculation - polymer) which is preserved during the formation of the paper sheet, which explains the improvement of the rigidity on the totality of the cellulosic substrate.
• the resistance to soiling can also be improved by the chemical nature of the polymer aggregates (s), in particular when they have a hydrophobic and / or oleophobic nature.
• the fibers used when they have a negative surface charge, these can be previously treated to promote the fixing of the cationic flocculation agent. We can then say that we add a preliminary step of "anionization" of the fibers.
• Such fibers may be cotton fibers.
• the cellulosic fibers of wood do not generally have this low negative surface charge. However, they may also be subject to this prior treatment, where appropriate.
• this preliminary step may consist in the addition of cellulose derivatives such as carboxymethylcellulose (CMC).
• CMC carboxymethylcellulose
• Such polymers capable of increasing the negative surface charge of fibers may in any case be chosen from anionic polymers which are soluble in water and have an affinity with cellulose.
• the crosslinking phenomenon is chemically translated by the formation of covalent bonds between two entities: a chemical compound and a crosslinking agent.
• the crosslinking agent composed of reactive groups, forms strong atomic bonds (of the order of 500 kJ / mol) with certain groups of the chemical compound according to a chemical reaction process taking place under specific energy conditions (temperature, pressure, radiation. ..).
• the bonds formed are homogeneously distributed. They are permanent and resistant, which gives the compound / crosslinking mixture rigidity and homogeneous dimensional stability, properties which are the opposite of those sought for a security sheet contemplated by the invention which must be flexible and resistant.
• Flocculation has the advantage of providing stiffness over the entire cellulosic substrate, in particular by virtue of the good distribution of the aggregates of polymer (s) in the substrate. It should also be noted that large amounts of polymer (s) are not necessary to achieve this improvement of the rigidity property.
• the surfacing by the same polymer has the disadvantage of leading to a brittle layer structure, which resists poorly to circulation, including wrinkling.
• such a mass treatment makes it possible to envisage an additional surface treatment, in particular a protective treatment, for example of the antifouling type and / or printing treatment, on the security sheet obtained according to the process of the invention.
• an additional surface treatment in particular a protective treatment, for example of the antifouling type and / or printing treatment
• the surface treatments do not make it so easy to carry out additional surface treatment for obvious reasons of surface affinities between them and modification of the properties provided by the first surface treatment, which must first be taken into account. account.
• the present invention relates to a wrinkle and crease-resistant security sheet comprising fibers, obtained by mass treatment of said fibers by a flocculation system, said flocculation system comprising an anionic dispersion of at least one polymer having a glass transition temperature above 23 ° C and a cationic flocculating agent.
• the invention relates to a wrinkle-resistant security sheet comprising fibers, said fibers comprising en masse aggregates of particles formed following the flocculation of an anionic dispersion of at least one polymer having a glass transition temperature above 23 ° C, and a cationic flocculation agent.
• the security sheet according to the invention comprises fibers.
• total fiber weight should be understood as meaning “ total dry fiber weight " unless otherwise indicated.
• the fibers used in the composition of the sheet comprise natural fibers.
• cellulosic fibers such as wood fibers, for example of eucalyptus, of softwood or their mixture, of cotton, bamboo, viscose, straw, abaca, asperto , hemp, jute, flax, sisal or their mixtures.
• the fibers may be bleached, semi-bleached or unbleached.
• the fibers in the composition of the sheet comprise cellulosic fibers, particularly cotton fibers.
• the fibers comprise fibers previously anionized with polymers capable of increasing the negative surface charge of the fibers such as anionic polymers which are soluble in water and have an affinity with cellulose.
• anionic polymers may be chosen from cellulose derivatives such as carboxymethylcellulose (CMC).
• said cellulosic fibers are present in a proportion greater than 60% by dry weight relative to the total dry weight of fibers and polymer (s), in particular in a proportion of greater than 70%.
• said cellulosic fibers represent at least 70% by dry weight of the total amount of fibers.
• said cellulosic fibers are cotton fibers and represent at least 70% by dry weight of the total amount of fibers.
• the fibers used in the composition of the sheet may comprise synthetic fibers.
• This embodiment is particularly advantageous because it makes it possible to further improve the tear-resistance properties of the sheet according to the invention.
• the Applicant has found that, surprisingly, the use of synthetic fibers, generally used to strengthen the paper, has a synergistic effect with the use according to the invention of a polymer presenting a specific Tg. Indeed, the Applicant has measured that the sheets containing synthetic fibers, while being rigid and retaining resistance to creasing and high soiling, also had a particularly high tear resistance.
• the tear resistance of the sheets according to this particular embodiment of the invention is greater than the tear resistance of the sheets according to the invention without synthetic fibers and the tear resistance of sheets comprising synthetic fibers. but no aggregates of polymer (s).
• the synthetic fibers are in a proportion of between 5% and 30% by dry weight relative to the total dry weight of fibers and polymer (s), and better still between 10% and 15% by weight. %.
• the sheet comprises cotton fibers in a proportion of at least 70% by dry weight relative to the total weight of the fibers and synthetic fibers in a proportion of between 10% and 30% by weight. % by dry weight relative to the total weight of the fibers, the sum total of the cotton fibers and synthetic fibers being equal to 100.
• said synthetic fibers are chosen from polyester, polyamide, rayon and viscose fibers, preferably they are polyamide fibers and / or polyester fibers. It may be, for example, polyamide 6-6 fibers or polyester fibers marketed by Kuraray under the trade name EP133®.
• a security sheet according to the invention further comprises at least polymer aggregates (s) having a glass transition temperature (Tg) greater than 23 ° C.
• the polymer (s) used in the context of the present invention have a glass transition temperature greater than 35 ° C, and more preferably greater than 40 ° C.
• glass transition temperature means the temperature below which the polymer is rigid. As the temperature increases, the polymer passes through a transition state that allows free macromolecular chains amorphous domains to slide relative to each other and the polymer softens.
• the measurement of the glass transition temperature can be carried out by differential scanning calorimetry (" Differential Scanning Calorimetry " or " DSC").
• the polymer (s) may be present in a proportion of between 1% and 40% by dry weight, in in particular between 2% and 25% by dry weight, and preferably between 2% and 15% by dry weight, relative to the total dry weight of fibers and polymer (s).
• the polymer (s) having a glass transition temperature greater than 23 ° C are chosen from polyacrylics, polyacrylates, polyacrylamides, polystyrenes, polyurethanes, polyvinyls, polyethylenes, and mixtures thereof.
• the polymer (s) having a glass transition temperature greater than 23 ° C. are chosen from acrylic (or polyacrylic) polymers, that is to say homopolymers or copolymers comprising at least less an acrylic monomer, namely acrylic homopolymers or acrylic copolymers.
• the polymer (s) having a glass transition temperature greater than 23 ° C. are chosen from acrylic homopolymers.
• the polymer (s) may be non-crosslinkable, crosslinkable with the aid of an external crosslinking agent or else self-crosslinkable.
• the polymer (s) are self-crosslinkable.
• the drying step may lead to crosslinking of the polymers, in a step subsequent to the implementation of the process according to the invention.
• the anionic dispersion of the polymer (s) is monophasic or multiphasic.
• a multiphasic dispersion corresponds in particular to core-shell particles comprising two types of polymers of which at least the most abundant (the core) is a rigid polymer considered according to the invention.
• the other polymer (s) may have a function other than the addition of rigidity, it (s) may (in particular) be used as crosslinking agent and / or binder.
• a security sheet according to the invention further comprises at least an effective amount of a cationic flocculation agent, said main agent.
• the term " effective amount” means the amount of cationic flocculating agent advantageously required to allow the anionic dispersion of the polymer to flocculate. This amount of cationic flocculating agent is to be considered with regard to the associated polymer (s) and may therefore vary from one polymer to another. From his general knowledge, the skilled person is able to adjust the amount of cationic flocculating agent necessary to allow flocculation of the polymer (s).
• the cationic flocculating agent called the main agent
• the main agent is present in an amount of between 0.5% and 5% by dry weight, in particular between 1% and 3% by dry weight, relative to the total dry weight. fiber and polymer (s).
• the cationic flocculating agent, said main agent, present in the security sheet according to the invention is chosen from water-soluble cationic polymers, in particular from polyacrylamides, polyethyleneimines, polyvinylamines and their mixtures.
• the cationic flocculating agent is a cationic resin.
• this resin is a polyamide-amine-epichloridin resin, called PAAE resin.
• the cationic flocculation agent is selected from polyacrylamides, polyethyleneimines, polyvinylamines and mixtures thereof.
• the security sheet comprises, in addition to the cationic flocculating agent, said main agent, described above, a secondary cationic flocculating agent, said secondary agent.
• Such a secondary cationic flocculating agent is present in an amount of between 0.1% and 0.5% by dry weight relative to the total dry weight of fibers and polymer (s).
• said cationic flocculation agent is selected from polyacrylamides, polyethylenimines, polyvinylamines and mixtures thereof.
• the security sheet comprises at least one security element.
• said security element is chosen from optically variable devices (OVD), in particular interference-effect elements, in particular iridescent elements, holograms, liquid crystals and interferential multilayer structures.
• OLED optically variable devices
• interference-effect elements in particular iridescent elements, holograms, liquid crystals and interferential multilayer structures.
• the sheet according to the invention may comprise an RFID device (radio frequency identification device).
• the security sheet comprises at least one at least partially fiber-free zone, also known as a " window " zone .
• the security sheet according to the invention comprises an embedded security thread or strip (e), in particular totally or partially, in said sheet, and preferably appearing in at least one window.
• the security sheet comprises mineral fillers in an amount of 1% to 10% by dry weight relative to the total dry weight of the composition of the sheet.
• said mineral fillers are present in a proportion of between 1% and 5% by dry weight relative to the total dry weight of the composition of the sheet.
• fillers are chosen, for example, from calcium carbonate, kaolin, titanium dioxide or mixtures thereof.
• the security sheet according to the invention may further comprise fillers and additives commonly used in the paper industry.
• the security sheet according to The invention further comprises carboxymethylcellulose (CMC).
• CMC carboxymethylcellulose
• the security sheet may further comprise an additional treatment, in particular an impregnation, an external surfacing layer, a coating or a coating. It can be an external treatment.
• surfacing layers coated on at least one side of a sheet, are well known to those skilled in the art and make it possible, for example for a layer based on a polyvinyl alcohol, to improve the properties of double strength. -plugging and pulling the leaf.
• the security sheet according to the invention may comprise a surfacing layer intended to reinforce its durability properties, such as, for example, a layer whose composition is described in the application EP 1 319 104 and which comprises a transparent or translucent elastomeric binder, such as a polyurethane, and a colloidal silica.
• a surfacing layer intended to reinforce its durability properties, such as, for example, a layer whose composition is described in the application EP 1 319 104 and which comprises a transparent or translucent elastomeric binder, such as a polyurethane, and a colloidal silica.
• the security sheet according to the invention further comprises an outer surfacing layer, preferably based on a polyvinyl alcohol, an acrylic polymer or a transparent or translucent elastomeric binder. , such as a polyurethane, and optionally a colloidal silica.
• the invention also relates to a method of manufacturing the security sheet described above.
• said fibers, said anionic dispersion of at least one polymer having a glass transition temperature greater than 23 ° C and said cationic flocculating agent are advantageously mixed in bulk.
• said polymer aggregates (s) are formed by contacting the anionic dispersion of polymer (s) with the fibers and the flocculation agent.
• said aqueous suspension further comprises an auxiliary cationic flocculating agent, said secondary agent, in an amount of between 0.1% and 0.5% by dry weight relative to the total dry weight fiber and polymer (s).
• the process of the invention makes it possible, by using polymer (s) having a specific Tg and flocculation agent (s), to flocculate the polymer (s) on the fibers and to obtain a very rigid safety sheet with particularly high resistance to creasing and soiling.
• the anionic dispersion of the polymer (s) having a glass transition temperature greater than 23 ° C and the cationic flocculating agent, said main agent are mixed in mass in the fibrous suspension before dewatering .
• said aqueous suspension is obtained from a mixture of fibers and said cationic flocculation agent, said main agent, to which said anionic dispersion of polymer (s) and optionally said cationic flocculation agent, said secondary agent, before proceeding with the formation of said sheet.
• This embodiment has the advantage of bringing the polymer (s) and the flocculation agent into contact in order to facilitate flocculation.
• This embodiment also has the advantage that it can be applied to aqueous suspensions of "standard " fibers used for the manufacture of safety sheets because they include wet strength agents which can also be used as main flocculation in the context of the present invention.
• crosslinking can take place after flocculation.
• the polymers, once flocculated can crosslink under the effect of the high temperature dedicated to drying.
• the method of manufacturing the security sheet comprises a step in which at least one face of said sheet, after dewatering of said suspension is coated with a surfacing layer.
• This surfacing layer may allow, for example, to improve the marked bending and / or tensile strength properties or even the durability properties of said sheet, as described above.
• the invention also relates to a security document comprising the security sheet object of the invention, or as obtained by the method of the invention, described above.
• the invention relates to a means of payment, such as a bank note, a payment card, a check or a restaurant ticket, an identity document, such as an identity card, a visa, a passport or a driving license, a card, including access, a lottery ticket, a ticket or a ticket to cultural or sports events, a loyalty card, a service card, a ticket a membership card, a playing or collectible card, a voucher or a voucher.
• a means of payment such as a bank note, a payment card, a check or a restaurant ticket, an identity document, such as an identity card, a visa, a passport or a driving license, a card, including access, a lottery ticket, a ticket or a ticket to cultural or sports events, a loyalty card, a service card, a ticket a membership card, a playing or collectible card, a voucher or a voucher.
• banknote This is preferably a bank note.
• One of the specificities of banknotes is indeed to be subjected to wrinkles and marked folds, and to have to maintain its rigidity and good resistance to wrinkles and creases marked despite the effects of traffic to minimize rejects in automatic machines and automatic sorting machines.
• a banknote generally has a thickness of between 70 ⁇ m and 170 ⁇ m, for example 100 ⁇ m.
• the grammage measurements can be performed according to ISO 536.
• Thickness measurements can be made according to ISO 534.
• compositions are prepared for making the measurements.
• the first composition is prepared from the weight proportions indicated in Table 1 below: ⁇ i> ⁇ u> Table 1 ⁇ / u> ⁇ /i> compounds Weight (g) Distilled water 500 NaCl 5 Lactic acid 5 Urea 0.5 Histidine hydrochloride 0.5 Water Qs 1000
• the second composition is prepared from the weight proportions indicated in Table 2 below: ⁇ i> ⁇ u> Table 2 ⁇ / u> ⁇ /i> compounds Weight (g) Yellow iron oxide marketed by Lanxess under the name Bayferrox® 420 0.833 Brown iron oxide marketed by Lanxess under the name Bayferrox® 610 0.833 Carbon black sold by the company BASF under the name Black Microlite CK 0.083 Vermiculite 2D marketed by EFISOL 248.25
• the compounds of Table 2 are mixed using a Turbula mixer for 30 minutes in a plastic bottle with six large 20 mm diameter ceramic beads.
• the third composition is prepared from the weight proportions indicated in Table 3 below: ⁇ i> ⁇ u> Table 3 ⁇ / u> ⁇ /i> compounds Weight (g) Lanolin marketed by Lanolines de la Tossée under the name Lanoline Lanor TEC 200 Ethoxylated tridecyl alcohol marketed by the company Nopco under the name Disponil® TD 0785 20
• the mixture of the two compounds of Table 3 is homogenized until the lanolin melts. 28 g of water are then added with stirring, followed by 16 g of ethoxylated ether of behenic alcohol (sold by the company Nopco under the name Eumulgin® BA 10). The whole is mixed by heating until a homogeneous preparation.
• the mixture is then allowed to cool to room temperature and then 24 g of water are then added by mixing for 15 minutes. 190 g of water are then added, incorporating it very slowly at the beginning.
• Each sample is crumpled beforehand 4 times with an IGT creasing device.
• the samples (75 mm x 140 mm) are mounted on wooden blocks (60 mm x 35 mm x 35 mm), around which they are held with three exposed faces.
• composition A 90 ml of composition A, 10 g of composition B, 20 g of composition C and 25 ceramic beads with a maximum diameter of 20 mm are placed in a plastic jar of 2 L.
• the ceramic beads may be alumina beads, they must not weigh less than 300 g. They are packaged before use by placing them in the Turbula mixer with an abrasive cream and a little water for 1 hour and 30 minutes.
• the mixture is agitated then the four wooden blocks, dry, on which the samples were placed are introduced.
• the jar is closed and stirred with a Turbula mixer at 67 rpm for 20 minutes.
• the samples are then rinsed with running water and dried using two blotters. They are then put in the oven at 60 ° C for 3 minutes.
• the samples are then calendered one by one with one passage per side, at 15 bar pressure, at minimum speed.
• the whiteness is an average value of three measurements according to the NF ISO 2470-2 6167 standard and the degree of yellowing is an average value of three measurements, which are well known to those skilled in the art (measurements carried out with the Datacolor Elrepho 3000 apparatus of the company Lorentzen & Wettre).
• flexural strength in Newton
• rigidity measurements can be made according to the ISO 2493-1 standard, in particular with a Taber stiffener (Model 150-B) or with a Franck rigidimeter ( Model 58565).
• the index of flexural strength (Nm 6 / Kg 3 ) is determined by taking into account the basis weight of the paper.
• the sheets according to the invention advantageously have a stiffness gain of at least 15%, or even at least 20%, with respect to the rigidity of a sheet comprising 100% cotton fibers.
• the double-fold resistance measurements can be carried out according to the ISO 5626 standard.
• Tear resistance measurements can be made according to ISO 1974.
• the tear index is obtained by dividing the tear strength by the basis weight.
• BENDTSEN porosity measurements can be made before and after creasing.
• the wrinkling operation causes, because of the folds formed, more or less pronounced alteration of the surface of the paper, leading to an increase in its porosity and therefore its fragility. Comparing the value of the porosity of the paper before and after creasing can therefore be evaluated the crease resistance of the latter. The less the increase in porosity between the initial sheet and the crumpled sheet, the less the paper is wrinkle resistant. The goal is therefore to obtain values of porosity after crumpling the lowest possible.
• the wrinkle test therefore makes it possible to determine the wrinkle resistance of papers such as bank note papers and wrapping papers.
• the apparatus used corresponds to that described by the National Bureau Of Standards ( Carson, FT Shaw, MB Wearing quality of experimental currency type papers, J. Research NBS 36, 256-257 (1946) RP 1701 ).
• the crumpling force is adjusted by the position of the weight on the arm of the lever, so that the pressure on the piston is 10 kg / cm 2 ⁇ 0.1 kg / cm 2 .
• Sampling and conditioning of the specimens are done in accordance with standards NFQ 03-009 and NFQ 03-010.
• the specimens can be measured as such. Since the specimen is constantly handled, it is necessary, in order to avoid moisture exchange with the operator, that the operator wears gloves of a moisture-barrier material during the preparation of the specimens and the run the test.
• test pieces are cut using a template. The running direction is marked on each specimen.
• the tube, closed lid, is then slid in continuity with the sleeve and the rolled test piece is transferred there by a return movement of the fork.
• the tube held by the lid with one hand, is then placed in a vertical position on the piston.
• the crumpling is done by pressing on the cover until the end of the long arm of the lever is raised above its rest position. It is important that the pressure exerted is sufficient to lift the weight, but neither too strong nor too fast for the lever to come into abutment.
• One way to control the effort is to use both hands on each other to press the lid.
• the lid is open and the test piece is crumpled in the shape of a small accordion, and out of the tube. It is put flat by carefully straightening the hand: acting too abruptly could produce notches on the side that would lead to tearing of the specimen.
• the straightened specimen is presented again for rolling in front of the slot of the sleeve but rotated 90 ° with respect to the first introduction; the complete cycle is repeated.
• the air permeability of each specimen is measured before and after wrinkling using a BENDTSEN porosimeter according to ISO 5636-3.
• the porosity is measured as follows: each specimen is straightened until it is reasonably flat. This can easily be done by holding between thumb and forefinger, the test piece by two opposite sides and then stretching it in three or four places. This operation is repeated by the other two sides; to do this operation in all four times is usually sufficient to obtain a sufficiently flat specimen.
• each specimen is introduced between the jaws of the clamping device of a brightness meter and is applied during two seconds enough pressure to mark the paper. Porosity is measured by ensuring that the BENDTSEN porosimeter head is centered on the surface squeezed to the brightnessometer.
• test pieces to be tested depends on the sample studied.
• the reproducibility of the test is such that a sample per sample sheet is sufficient.
• the porosity of the sheets according to the invention after creasing can vary from 1 to 20 ml / min, in particular from 1 to 12 ml / min.
• the sheets A to F, and 1 to 3, tested below, are prepared according to the standard paper-making process, that is to say, in particular by draining, pressing and then drying aqueous suspensions whose compositions in dry weight are given in the tables. 1 to 3 below.
• PAAE resin polyamide-amine-epichloridrine resin
• a flocculation step is carried out in Examples B, C and 1 to 3.
• the PAAE resin has a role of cationic flocculation agent and also resistance to corrosion. wet state.
• Said sheets then undergo, according to a common practice in the paper industry, an external surfacing, as described above, deposited at a rate of 5 g / m 2 / face. Said surfacing is carried out by impregnation.
• the sheets A to C are impregnated with a layer based on a polyvinyl alcohol (PVA).
• Sheets D and E and 1 to 3 are impregnated with a layer based on a polyvinyl alcohol (PVA).
• As for the sheet C it is impregnated with a layer based on an acrylic polymer having a Tg of 38 ° C.
• the sheets E, F and 3 have, before surfacing, a basis weight of 85 g / m 2 .
• Comparative Example A relates to standard, untreated paper.
• Comparative Example B relates to a sheet obtained according to the process as described in document WO 2008/152299 .
• Comparative example C relates to a sheet obtained according to the process as described in the document WO 2014/083527 .
• the sheets of Examples 1 and 2 according to the invention have a clear rigidity gain compared to the sheet of Comparative Example D.
• sheets of Examples 1 and 2 show an improvement in the soiling index of 4 to 5 points.
• the sheet of Example 3 according to the invention has a much higher rigidity than that of Comparative Example E, while exhibiting values of tensile strength, tear strength and double-fold comparable to those of Comparative Example E, which shows that the use of the polymers according to the invention does not degrade the properties of tensile strength, tear and double-fold.
• Example F Comparison of Example F with Example 3 makes it possible to show that the surfacing of a rigid acrylic polymer does not improve the rigidity of the substrate, despite the large amount of polymer supplied (6 g / m 2 against 1.5 g / m 2 of PVA).

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• 2014
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