EP1623072A1 - Procede de traitement au plasma du papier et du carton - Google Patents

Procede de traitement au plasma du papier et du carton

Info

Publication number
EP1623072A1
EP1623072A1 EP03727948A EP03727948A EP1623072A1 EP 1623072 A1 EP1623072 A1 EP 1623072A1 EP 03727948 A EP03727948 A EP 03727948A EP 03727948 A EP03727948 A EP 03727948A EP 1623072 A1 EP1623072 A1 EP 1623072A1
Authority
EP
European Patent Office
Prior art keywords
plasma
paper
cardboard
mbar
treatment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03727948A
Other languages
German (de)
English (en)
Inventor
C. Univ. Degli Studi di Milano-Bicocca RICCARDI
Marco Uni. Degli Studi di Milano-Bicocca ORLANDI
Antonino Raffaele Addamo
Claudio Bozzi
Bruno Marcandalli
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stazione Sperimentale Carta Cartoni E Paste Per Carte
Universita degli Studi di Milano Bicocca
Original Assignee
Stazione Sperimentale Carta Cartoni E Paste Per Carte
Universita degli Studi di Milano Bicocca
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Stazione Sperimentale Carta Cartoni E Paste Per Carte, Universita degli Studi di Milano Bicocca filed Critical Stazione Sperimentale Carta Cartoni E Paste Per Carte
Publication of EP1623072A1 publication Critical patent/EP1623072A1/fr
Withdrawn legal-status Critical Current

Links

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
    • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
    • D21H25/04—Physical treatment, e.g. heating, irradiating
    • 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
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/30—Pretreatment of the paper

Definitions

  • the invention relates to a method for the treatment of paper, cardboard and associated fibres, in particular to a method which enables new surface characteristics of the materials mentioned above to be improved or simply obtained.
  • paper is a hydrophilic material because the cellulose fibre, which is the main component, is a hydrophilic polymer.
  • Cellulose the most important and abundant biopolymer known, is a polydispersed linear polymer composed of molecules of glucopyranose (glucose) bonded to each other by a 1-4 ⁇ -glucoside bond.
  • Each individual unit of glucose in the polymer chain exhibits three free hydroxyl groups capable of forming intra-intermolecular bonds, which cause the cellulose molecules to aggregate into microfibrils, which exhibit highly ordered (crystalline) or less ordered (amorphous) areas.
  • the hydroxyl groups in the amorphous regions of the cellulose are capable of interacting with water and are responsible for the hydrophilic properties of the cellulose fibres.
  • the packaging of a product may be defined as "in the product, everything which is not the product itself” or, in other words, any wrapping or container for containing, shipping and storing the product.
  • the main functions of the packaging are: to ensure the integrity of the product until the time of its use (containing, transporting and mechanical protection) , to attract the consumer, to facilitate disposal after consumption in an ecologically acceptable manner, safeguarding the environment.
  • Packaging is generally classified in three categories :
  • PCBs heavy metals
  • tissue sector that is household papers such as for example ScottexTM, paper handkerchiefs and toilet paper
  • ScottexTM a paper handkerchiefs and toilet paper
  • SAPs ultra-absorbent polymers
  • tissue produced from plastic material with micro-perforations to allow the liquid to flow towards the fluff, with a micro- perforated paper with water-repellent characteristics.
  • a further sector in which paper, cardboard and derivative cellulose fibres are used is that of self- adhesive labels.
  • a self-adhesive label consists basically of a support or backing which is first siliconized and then treated with adhesive, and then laminated with another material which represents the actual surface on which the label will then be printed.
  • the adhesive is transferred from the anti-adhesive support to the front, that is the label itself.
  • the papers which constitute the backing are generally very smooth papers, and therefore in this case a particularly suitable paper support must be produced.
  • papers joined (laminated) with films of polymer (for example polyethylene) , glazed papers or polymer films are used.
  • the front the label which is removed from the backing, may consist of glazed paper, metallized or laminated papers, plastic films or heavily sized papers since they must have good water resistance.
  • cellulose is a highly crystalline polymer, relatively inert during chemical treatment and soluble only in a few solvents.
  • the most common solvents are copper ethylene diamine (CED) , and cadmium ethylene diamine (Cadoxen) , while among those less well-known mention may be made of N-methylmorpholine, the N-oxide of nitrogen and dimethlyformamide chloride.
  • the grafting of a synthetic polymer to the cellulose is certainly one of the methods studied and is important because it enables a material to be produced combining the properties of the original polymers.
  • the grafting reaction is generally carried out in a heterogeneous gas-solid or liquid-solid system in which the solid cellulose polymer is brought into contact with a monomer in gaseous or liquid phase . It is clear that the monomer will react both with the cellulose and with itself to form the polymer.
  • the grafting can also be carried out in homogeneous conditions - and therefore with solvents capable of solubilizing cellulose. In the majority of cases, the polymerization reaction is a radical reaction.
  • Another route is to produce a polymer mix. In this case too, however, as it is not possible to melt the cellulose, it is necessary to use solvents capable of solubilizing both the cellulose and the synthetic polymer .
  • the roughness characteristics (smoothness) and porosity of the surface are particularly important since they affect the absorption properties.
  • papers known as "sized" papers are produced by adding to the initial mix additives such as for example diketenes, alkyl succinic anhydrides, PACs (poly-aluminium chlorides) .
  • the same products, dispersed in an aqueous solution may be spread on the surface, with additional plant and energy costs.
  • Oil-repellent properties are added in the known technology by directly adjusting the formation of the sheet and/or with surface treatments using fluorinated products and/or by means of bulk treatments (addition of a chemical product to the mix from which the sheet is obtained) .
  • a further property of considerable importance is represented by the barrier to gases (for example water vapour, C0 2 and N 2 ) which is usually obtained using plastic and/or metal films.
  • gases for example water vapour, C0 2 and N 2
  • plastic and/or metal films In the case of paper and cardboard, widespread use is made of multi-layer or joined materials which combine the cellulose product with plastic and/or metal films .
  • These properties comprise for example adhesion to bio-polymers, synthetic polymers, inks, colours and resins.
  • these properties may be obtained using conventional methods, that is by means of chemical reactions or surface treatments (glazing, coating) .
  • pulping of the paper is the main method used for complete reuse of the fibres.
  • a crucial point in de-inking is the size of the ink particles adsorbed on the sheet.
  • Other important points for de-inking relate to the chemical structure (composition) of the fibres and the type of ink, whether liquid (ink jet printers) or solid (photocopies, laser printers) .
  • the main mechanism for de-inking paper originating from cellulose fibres is rolling-up followed by solubilizing of the ink particles.
  • plasma treatment would avoid or at least reduce the use of large quantities of water and also of compounds which are polluting and harmful to health.
  • the problem addressed by the invention is therefore to devise a method for the treatment of paper, cardboard and associated fibres which offers characteristics such as to satisfy the above-mentioned requirements and at the same time obviating the numerous disadvantages exhibited by the methods for treating these materials using the known techniques mentioned above, and also to find an alternative method to some of the above-mentioned treatments.
  • This problem is solved by a method of treatment in accordance with the appended claims .
  • the method for working card, cardboard and associated fibres comprises at least one step of treatment with cold plasma in which during this step of plasma treatment the emission of gas from the surface of said paper, cardboard or associated fibres is controlled from time to time, depending on the type, of materials and the particular conditions of treatment, so that it does not substantially affect the plasma treatment.
  • the above-mentioned method comprises successively or simultaneously a step of removing the gases adsorbed on the surface of said paper, cardboard and associated fibres and a step of plasma treatment of this surface.
  • the removal step may be performed by subjecting the substrate to be treated to a high vacuum in order to obtain a pressure less than or equal to 10 ⁇ 2 mbar per cm 3 /sec inside the treatment chamber, preferably less than 10 "4 mbar cm 3 /sec, still more preferably less than 5xl0 ⁇ 5 mbar cm 3 /sec.
  • said step of removal of the gases may be carried out by causing the treatment gas, during application of the plasma, to flow tangentially to the surface to be treated so as to "wash" the surface, that is remove the gases adsorbed on the surface. This is because the tangential flow of the gas, since it carries molecules and charges as explained previously, has the effect of removing the gases from the surface of the materials to be treated, clearing them away.
  • the emission of gas from the surface of the above-mentioned materials may be controlled by using a plasma source which generates substantially neutral particles .
  • the neutral particles have a contrary effect compared with the charged particles described above. The reason is that, precisely because of the substantial absence of charge, these particles do not remove the gases adsorbed by the surface of the materials to be treated, but prevent or at least reduce detachment of the gases so that they cannot adversely affect the plasma treatment .
  • An example of this further form of embodiment of the invention is the use of a plasma source modulated in power.
  • a plasma source modulated in power For example, by modulating the amplitude of the power of the source it is possible to strike and extinguish the plasma so as to minimize the flows of charged particles onto the surface of the substrate.
  • a plasma for short periods comprised between lO ⁇ s and 10ms
  • extinguishing the plasma for times comprised between lO ⁇ s and Is, it is possible to maximize the production of the neutral radical species and minimize those charges which produce chemical etching and therefore degassing.
  • the step of plasma treatment of the paper, cardboard and associated fibres can be carried out with all noble gases, preferably helium, argon, neon or a mixture of these with air or oxygen or hydrogen, inert gases such as nitrogen, for example and mixtures of these, fluorinated gases chosen from the group of fluorocarbons in particular CF 4 and CFC, WF 6 , XeF 2 , provided that it is not SF 6 already known from patent application PCT/IT02/00335, hydrocarbons, C0 2 , hydrogen, compounds of silicon, silanes, siloxanes and organosilanes, compounds of chlorine, acrylates, vinyl monomers, chloromethylsilane, metals and also corresponding mixtures or polymers.
  • noble gases preferably helium, argon, neon or a mixture of these with air or oxygen or hydrogen
  • inert gases such as nitrogen, for example and mixtures of these, fluorinated gases chosen from the group of fluorocarbons in particular CF 4 and CFC, WF
  • the treatment may be carried out by also using the above gases in . liquid solution provided that the respective vapour tensions are greater compared with the plasma production pressure.
  • the liquid solution has a lower vapour tension compared with the plasma production pressure (for example at atmospheric pressure) the solution is then vaporized in aerosol form.
  • the plasma used for treatment of the paper, cardboard and associated fibres, according to the invention is a cold plasma, that is the temperature of the total mass of gas in the plasma phase is of the same order as ambient temperature.
  • the cold plasma may be produced at pressures comprised between 10 "4 mbar and 100 mbar, or under vacuum as defined in the present description, or at pressures greater than 100 mbar and less than or equal to 2 atm, or of the order of the atmospheric pressure as defined in the present description.
  • the plasma may be generated using various electromagnetic sources, that is sources of various frequencies and various geometries.
  • the power emitted by the sources may be modulated in amplitude and/or in frequency so as to control, for example minimize or maximize, the local density of charged species on the surface of the specimen and then to select the type of treatment to be carried out depending on requirements or preferences, and at the same time control the phenomenon of degassing of the surface.
  • the physical-chemical processes which take place on the surface of the paper, cardboard and associated fibres also depend on the plasma parameters and the electrical potential values assumed by the specimen relative to the plasma potential, that is by the electric fields in the vicinity of the specimen.
  • the electric fields produce currents of positive or negative electrical charges which interact with the substrate by bombarding it or simply charging it electrically.
  • These electric fields may be controlled by polarizing the support of the specimen (or the specimen itself) , or by placing the specimen in the ion sheath which is created in the vicinity of the antenna, which assumes negative electrical potential values of some hundreds of volts
  • This method is adopted preferably for producing physical and chemical etching with the aim of cleaning the surface, removing the deposits, modifying the surface roughness and activating the surface.
  • the power of the source is modulated in amplitude, so as to pulse the plasma over short periods and minimize the flows of charges compared with those of the neutral species.
  • the plasma parameters are imposed by so-called discharge parameters, or by the parameters of the source such as, for example, the electrical power which is comprised between 0.1 /cm 2 and 50 W/cm 2 , the geometry of the source which produces the plasma (capacitive, inductive , source) , the frequencies of the electromagnetic radiation used to produce the plasma and the residual vacuum inside the chamber in which the treatment is carried out.
  • the vacuum in turn also depends on the level of residual humidity and on the degassing of the paper, cardboard and associated fibres, that is on the flows of volatile substances which escape from the materials and on the degassing of the internal structures which compose the reactor.
  • the flows of the gas must be tangent to the substrate, to "wash" the gases degassed during the process of the surface.
  • the substrate in some cases for example when thick and/or spongy materials have to be treated, it is advantageous also to maintain the substrate at a temperature below 70°C, preferably less than or equal to ambient temperature, to create differences in temperature and pressure between the plasma and the substrate, that is differences between the pressures of the substrate and of the plasma so as to promote orientation of the flows towards the substrate when treatment is required or, conversely, away from the substrate when it is wished to promote degassing before the plasma treatment .
  • the specimen may be located in the diffuse plasma region mounted on a floating support; (b) the specimen is mounted on a metal support which is polarized to some tens of volts (up to 100 V) negative or positive to promote ion bombardment on its surface; (c) the specimen is positioned in the ion sheath which is created close to the plasma source; (d) the specimen is set in motion so that the treatment can be made homogeneous .
  • the treatment time for the paper, cardboard and associated fibres in a cold plasma generally does not exceed 20 minutes, preferably is less than 15 minutes, still more preferably is less than 5 minutes.
  • said treatment is carried out under vacuum or at atmospheric pressure.
  • the cold plasma is produced in chambers containing gases at pressure values which may vary between 10 "4 mbar and 100 mbar.
  • the above-mentioned type of plasma under vacuum may be used according to discontinuous, continuous and semi-continuous methods and using the roll-to-roll method.
  • the discontinuous method provides for a first and a second step in which in the first step the specimen is placed in a chamber which is evacuated to pressures lower than that of the gas used.
  • the gas is air present inside the chamber, said air is evacuated to create a vacuum down to the pressure value at which the plasma treatment is carried out.
  • the plasma is produced and the plasma treatment carried out .
  • the method comprises a third treatment step, in which immediately after or during the plasma treatment, the specimen is made to interact with gases of various types, such as for example polymer gases or polymers in the gaseous phase .
  • degassing is done by making the gas flow tangentially to the specimen and/or pulsing the plasma.
  • the action of flushing with pulsed plasma causes an optimum synergistic effect from the point of view of the results .
  • the plasma may be produced using various electromagnetic sources, that is with sources of various frequencies.
  • the process operating conditions are controlled by measuring the plasma parameters and the physical-chemical properties of the specimens.
  • Treatment times are less than 20 minutes and the treatment may be repeated several times .
  • the paper, cardboard and associated fibres may be left for various lengths of time in an atmosphere of air or inert or active gas and then subjected to another treatment with the same gas or a different gas.
  • the semi-continuous method is preferred for limited quantities of material, or pieces or manufactured items of paper and cardboard or fibres used in the paper industry.
  • an installation composed of a plurality of chambers may be used, for example a loading and evacuation chamber, the next one for plasma treatment, and the last for evacuation and unloading of the material .
  • the chambers may be connected by connecting passages (ducts) open or isolated by vacuum valves.
  • guards or intermediate spaces are provided between the adjacent chambers capable of isolating the chambers.
  • degassing may be advantageously solved by pulsing the plasma and/or causing gas to flow onto the surface and/or applying a dry . gas treatment in the chamber preceding the one where the plasma is produced.
  • the material is treated and, after the treatment which lasts less than 20 minutes, is transferred to the evacuation and unloading chamber which is at a lower pressure than the treatment pressure.
  • the material may also once again be kept in an atmosphere of gas other than air. Then the evacuation and unloading chamber is opened and the material is unloaded.
  • this last chamber is again evacuated and the cycle is repeated.
  • the treatments are different, that is with different gases, or the treatments are cyclic, the material may be treated either in a single chamber or in a system of a plurality of treatment chambers. These chambers are intermediate between the loading and evacuation chamber and the evacuation and unloading chamber. Or, in cyclic treatments, the material may be left in suitable chambers and then be treated again.
  • This method may be used for fibres used in the paper industry, pieces of paper and cardboards, manufactured items of paper and cardboard. It must be stressed that during the treatment in the plasma chamber, the manufactured items or fibres may be set in motion so as to make the treatment homogeneous.
  • the continuous method may be carried out using various procedures which are given below.
  • the roll-to-roll system applies preferably to paper and cardboard materials which can be rolled.
  • the system in question is a system of rolling and unrolling in a process chamber isolated from the surrounding environment.
  • the roll-to-roll treatment takes place in a low pressure chamber in which the paper is unrolled and drawn into the plasma for the process and then rolled up again inside the vacuum chamber.
  • This system is constituted by a vacuum chamber which can be evacuated by means of a pumping system and in which a flow of gas at the desired pressure can be maintained.
  • a transmission system for example a radiofrequency or microwave system, or simply by static or low frequency electric fields.
  • the systems for producing a' plasma are similar to those described previously.
  • the continuous process may take place in a treatment chamber in which paper materials are drawn continuously into said chamber from the outside through seals which improve the sealing between the ambient pressure and the vacuum in the chamber. In this configuration, the material enters and exits through the seals and the process takes place continuously.
  • a vacuum plant of this type must provide various pumping chambers to obtain the vacuum.
  • This technique may be applied " to any of the above-mentioned materials and for any intended use and may be carried out with any cold plasma reactor, with the aim of improving or modifying the surface characteristics without impairing the bulk characteristics obtained with the previous working operations, and also the natural characteristics intrinsic to the materials themselves.
  • the cold plasma produced at atmospheric pressure may preferably be of the corona type.
  • the plasma is produced at low frequency or at a frequency comprised between 1 and 200 kHz, at a pressure around atmospheric pressure as specified previously, between two conducting electrodes or one conductor and one dielectric or two dielectrics, or two conductors coated with dielectric.
  • the paper, cardboard and associated fibres are placed at a distance from the electrodes which varies from 0.2 cm to 3 cm.
  • the specimen may move with respect to the source using the system such as the roll-to-roll described above at variable speeds, and also the treatment time can be varied as desired.
  • the power levels used may for example be of the order of 300 W for a length of 20 cm of paper, while the pressure is close to atmospheric pressure, or within the interval specified previously.
  • the surface of the material is cleaned (and degassed) with inert gas or dry air or undergoes a preliminary drying process .
  • the speeds of the material are between 1 m/minute and 100 m/minute, the power is comprised between 50 W and 2 kW and the frequencies are comprised between 1kHz and 200 kHz.
  • the material may be treated from one to a plurality of times, though for times of less than a second each time so as to avoid the damage mentioned above.
  • the materials may be covered with gases of various types, that is other than air.
  • the corona treatment is carried out in a controlled atmosphere chamber and the gas is made to flow near the electrodes or by means of the electrode itself.
  • the method for working paper, cardboard and associated fibres comprises at least one step of treatment with cold plasma in which during said plasma treatment step the emission of gas from the surface of said paper, cardboard and associated fibres is controlled from time to time, depending on the type of materials and particular conditions of treatment, so that it does. not significantly affect the plasma treatment.
  • the gas emissions may be controlled by subjecting the specimen to be treated to a high vacuum before the plasma step.
  • the degassing flow may be controlled by applying a pressure equal to or less than 10 "2 mbar, preferably equal to or less than 10 "4 mbar, still more preferably equal to or less than 5xl0 "5 mbar.
  • the treatment with plasma is carried out before any of the steps of working the paper, or cardboard following the drying step, while for the fibres, the treatment is applied before and after the steps which involve the use of water or other solvents .
  • This technique may be applied to any type of paper, cardboard and associated fibres and for any intended use and can be carried out with any cold plasma reactor, with the aim of improving or modifying the surface characteristics without impairing the bulk characteristics obtained with the previous working operations, or the natural characteristics intrinsic to the paper, cardboard or associated fibres.
  • the plasma . treatment step may preferably comprise the following steps individually or in any combination: :
  • a thin film for example of metals, polymers, organic and inorganic material oh the surface of the material
  • the method of treating the material comprises a step of applying the plasma to the surface of the material in order to improve it or provide it with new properties.
  • the advantages of the method of working according . to the invention compared with conventional surface treatment may be summarized as follows :
  • plasmas of noble gases include plasmas of noble gases, inert gases and, preferably, oxygen, air, chlorine, ammonia, fluorinated gases mentioned above, hydrogen, nitrogen, argon, helium, neon and mixtures of these.
  • the material treatment chamber is evacuated so as to obtain pressures comprised between 0.1 and 2 mbar.
  • the treatment chamber is evacuated so as to obtain pressures lower than the pressure at which the treatment is carried out and, consequently, to achieve adequate control of degassing.
  • the chamber is then filled with gas and the plasma generated, for example with a radiofrequency electromagnetic source, at a pressure comprised between 0.01 and 20 mbar, preferably comprised between 0.1 and 2 mbar, still more preferably between 0.2 mbar and 0.8 mbar and at an electron temperature comprised between 0.1 eV and 20 eV, preferably comprised between 1 eV and 15 eV, still more preferably between 2 eV and 10 eV.
  • the power used per unit of surface is comprised between 0.1 W/cm 2 and 50 W/cm 2 , preferably between 1 W/cm 2 and 10 W/cm 2 .
  • the plasma is applied to the surface of the material for times of less than 15 minutes, preferably less than 10 minutes, still more preferably between 30 seconds and 5 minutes.
  • the breakdown time of a drop of water was calculated, that is the time after which the 20 ⁇ l drop of water loses its shape and spreads over the surface of the material without yet being absorbed, and its absorption time on the surface of the material .
  • the breakdown time of a drop of water changes for example from 1 minute, in the case of paper not treated with plasma, to less than 1 second in the case of plasma treatment according to the invention, while the actual absorption time for a drop of water decreases from 5 minutes to less than 1 second.
  • the duration of the hydrophilia effects may in some cases be limited in time. Therefore, in the case where this process is used before the step of dyeing or coating, it may be necessary for the subsequent steps of re-wetting or dyeing or spreading to be carried out within the next two weeks .
  • a further advantage offered by the plasma treatment lies in the fact that the contact angle decreases substantially.
  • the contact angle is a parameter used in the industry to evaluate the wettability of a surface: the lower its value, the greater the wettability.
  • Residual pressure (after degassing): 5xl0 "3 mbar
  • Type of gas air under vacuum
  • Treatment with corona plasma comprising flushing
  • Duration of treatment 0.1 seconds repeated 5 times
  • the use of the plasma treatment according to the invention enables the surface of the material to be activated by breaking the chemical bonds and generating free radicals and the roughness of the surface to be modified.
  • a specimen of material is treated both with a plasma produced with a radiofrequency source under vacuum and with a plasma at atmospheric pressure.
  • the plasma is created with gases such as for example electronegative gases, oxygen, C0 2 , air, and with chlorine, hydrogen, ammonia, inert gases, noble gases, inert gases and mixtures of these.
  • gases such as for example electronegative gases, oxygen, C0 2 , air, and with chlorine, hydrogen, ammonia, inert gases, noble gases, inert gases and mixtures of these.
  • the specimen is mounted on a movable support placed in a chamber in which a vacuum is created to lower pressures compared with that of the plasma treatment which is less than 20 mbar.
  • the chamber is filled with gas to pressures which vary from 0.01 mbar to 20 mbar, preferably between 0.1 and 10 mbar, still more preferably between 0.2 and 3 mbar and the plasma is generated with a radiofrequency source for times of less than 15 minutes, preferably less than 10 minutes, still more preferably between 30 seconds and 5 minutes .
  • a corona plasma is used with treatment at atmospheric pressure with gas such as air, noble gases or inert gases for a time of less than one second repeated up to a maximum of 20 times.
  • the above-mentioned method increases the permanence of the colour on the paper, that is it gives better fixing and stability in time of the colour compared with those obtained using the methods of the known technology.
  • This method may be applied to facilitate recycling of the paper for example to facilitate or obtain de-inking of the paper to be recycled or to facilitate the removal of resins or chemical films from the surface.
  • the method for treatment of the paper, cardboard and fibres used in the paper industry comprising the application of plasma according to the invention may also be used for cleaning the surface of the paper, cardboard and fibres used in the paper industry.
  • gases such as, for example, noble gases, inert gases preferably including nitrogen, oxygen, air, chlorine, ammonia, hydrogen, fluorinated gases and mixtures of these may be used.
  • the plasma may be of the vacuum type or of the atmospheric pressure type.
  • the above-mentioned surface cleaning of the material may be carried out with a plasma under vacuum at a pressure comprised between 10 "4 mbar and 20 mbar, for a time of less than 20 minutes, preferably less than 10 minutes and still more preferably between 30 seconds and 5 minutes .
  • a plasma under vacuum at a pressure comprised between 10 "4 mbar and 20 mbar, for a time of less than 20 minutes, preferably less than 10 minutes and still more preferably between 30 seconds and 5 minutes .
  • the power to be used corresponds to that specified in the more general part of the present description.
  • the treatment time is reduced to no more than a few seconds and the surface is surprisingly uniform and hydrophilic.
  • the quantity of material removed is kept under control and is below 20 percent of the total weight.
  • This method may also be used in any case to remove resins from the surface of the paper.
  • a further use of the method for treating the paper, cardboard and fibres used in the paper industry comprising application of the cold plasma according to the invention lies in obtaining a water-repellent effect on the surface of the paper, cardboard and fibres used in the paper industry.
  • the plasma treatment may . be carried out by means of fluorinated gases in general, such as the fluorocarbons including for example CF 4 , CFC, or NF 3 and WF 6 , compounds of silicon, silane and siloxanes, organosilanes such as hexamethyldisiloxane, hydrocarbons and mixtures of these . .
  • fluorinated gases such as the fluorocarbons including for example CF 4 , CFC, or NF 3 and WF 6 , compounds of silicon, silane and siloxanes, organosilanes such as hexamethyldisiloxane, hydrocarbons and mixtures of these .
  • fluorocarbons and compounds of silicon, silane and siloxanes may be deposited to form a film on the surface of the paper, cardboard and fibres used in the paper industry so as to create said water-repellent effect.
  • These polymer films may be removed from the surface of the paper, cardboard and fibres used in the paper industry with loss of water-repellence. Therefore it is necessary for the thickness of these deposits to be optimized. This varies from specimen to specimen, since it depends on the roughness and capillarity of the specimen. Moreover it is important, in order for the deposit to have proper adhesion, to have a stable and clean surface, that is a surface in which degassing is particularly controlled and that it is activated at the same time.
  • fluorinated gases such as NF 3 , WF 6 and mixtures of these with hydrogen or noble gas
  • the surface of the material is covered with fluorine radicals which are grafted to form stable and lasting bonds but without forming a film.
  • organosilanes such as for example hexamethyldisiloxane
  • a film of the Si0 2 type of variable thickness is created on the surface.
  • the method of obtaining water-repellence is implemented preferably with fluorocarbons, or with gases which allow numerous fluorine-carbon bonds to form, and with organosilanes and mixtures of these.
  • the pressure is comprised between 0.1 and 10 mbar, preferably between 0.2 mbar and 5 mbar, still more preferably between 0.2 mbar and 3 mbar.
  • the electron plasma density is approximately 10 8 cm “3 while the ion plasma density reaches the value of 10 11 cm "3 .
  • Treatment time is less than 15 minutes, is preferably less than 10 minutes and still more preferably less than 5 minutes and the power corresponds to that specified previously.
  • the residual pressure when CF4 is used is preferably between 3xl0 "6 mbar and 5xl0 "5 mbar.
  • the distances of the specimen from the antenna may be between 5 cm and 7.5 cm.
  • the residual pressure is between 2xl0 "3 mbar and 8xl0 "3 mbar and the distance of the specimen from the antenna is between 3 cm and 6 cm.
  • the specimen of material may also be mounted on a movable support and placed in the chamber which is evacuated to pressures below that of the process gas, that is lower than the treatment pressure. Next, the chamber containing the specimen is filled with gas and the plasma is generated using a radiofrequency or low pressure source.
  • the water repellent effect on the paper, cardboard and fibres used in the paper industry does not depend on the source with which the plasma is produced and it can be obtained with radiofrequency, microwave or low frequency sources or with corona plasmas at a pressure of the order of atmospheric pressure, which contain numerous fluorine radicals or radicals originating from organosilanes.
  • the effectiveness and duration of the effect on the surface improves when the process uses a fluorinated gas which contains CF 4 and mixtures of this, hexamethyldisiloxane and mixtures of this, preferably with oxygen or air.
  • the power levels are comprised between 0.1 W/cm 2 and 20 W/cm 2 , preferably between 1 W/cm 2 and 10 W/cm 2 , still more preferably between lW/cm 2 and 5 W/cm 2 .
  • the plasma treatments with organosilanes and mixtures of these with oxygen show absorption times for a 20 ⁇ l water drop of more than 100 minutes (100 minutes is the time for which evaporation of the entire drop of water occurs, and therefore the drop of water evaporates) against absorption times which may vary between 0 seconds (for absorbent paper) to some minutes.
  • the roll-off angle is reduced to 10°. There are no traces of marks left by the drop of water such as swelling of the surface. The reduction in the roll-off angle means that a drop of water can slide far more easily. This process is useful for making paper, cardboard and the fibres used in the paper industry water-repellent without varying the taste and smell properties obtained with the previous treatments, and ensuring that they are lasting.
  • the deposits on the surface are less than one ⁇ m, preferably between lOnm and lOOnm. Moreover, gas permeability tests demonstrate that permeability to water vapour and oxygen is reduced.
  • the specimen not treated referred to as "untreated material” has a Cobb60 value of 860 g/m 2 .
  • the Cobb measurement is taken as follows. The specimen is placed in a cell (the base of the specimen holder is clamped onto the paper so as to prevent the escape of liquid from the base) and is covered with a layer of water 1 era in depth, for a specified time
  • the cell is emptied by pouring out, the specimen is extracted from the cell, quickly dried with absorbent paper to remove the unabsorbed water, and the specimen is weighed. The result is expressed in grams of water absorbed per square metre of surface of the material. It is obtained as the difference between the weight of the specimen after and before exposure to water.
  • the untreated material has an H 2 0 absorption time of 0 s, that is it is hydrophilic. On the untreated material, it is not possible to measure of the roll-off angle or the contact angle because the drop of water is absorbed immediately.
  • the specimen underwent ageing tests in an oven with a first stage at 50 degrees with a 100% humidity level for two hours and a second stage at 50 degrees.
  • the Cobb, contact angle, roll-off, and water drop absorption analyses carried out after the ageing tests gave the same values as those given in the table. In other words, the water-repellent effect remains unchanged and persists both in time and after the ageing tests.
  • the untreated material has an H 2 0 absorption time of 2 s (it is hydrophilic) .
  • Example 3 Material specimen of thin A-paper
  • the untreated material has an H 2 0 absorption time of 15 s.
  • Example 4 Material hospital card (cardboard for packaging)
  • the untreated material has an H 2 0 absorption time value of 30 s.
  • the Cobb value on the untreated material is 279.8 g/m 2 .
  • the assembly thus prepared is weighed (mi) and is placed in a dryer containing silica gel, coloured with an indicator, previously dried for 24 h at 100 °C and conditioned for 24 h at 23 ⁇ 2 °C with the dryer closed. After 24 hours, the container is removed and weighed again (m 2 ) .
  • the difference in weight m ⁇ -m 2 gives the amount of water passing in the form of vapour through the free area of the test piece, that is 1000 mm 2 of surface area.
  • the drier must remain in an environment at 23 ⁇ 2 °C.
  • the rate of transmission of the water vapour expressed in grams per square metre in 24 h, is then given by 1000 (m ⁇ -m 2 ) .
  • the results of the permeability measurements are given here by way of example for a specimen of absorbent paper.
  • the untreated material has a Cobb 6 o value of
  • the untreated material has an H 2 0 absorption time of 0 s .
  • the untreated material has an H 2 0 absorption time of 90 s.
  • the untreated material has a roll-off angle value of 26° .
  • the untreated material has an H 2 0 absorption time of 180 s.
  • the untreated material has a roll-off value of
  • the untreated material has an H 2 0 absorption time of 15 s.
  • the untreated material has a roll-off value of 34. TABLE 8
  • the deposits obtained with organosilanes and fluorocarbons also have properties of the barrier film type for water vapour and for gas .
  • the kit test is used.
  • the kit test is a completely conventional analysis which is applied to the specimen to evaluate the degree of oil-repellence. It is carried out by placing a drop of a mixture on the surface for 15 seconds and evaluating the penetration on the other side of the paper.
  • various grades of oil- repellence are defined, ranging from 1 to 12, 12 being the highest grade of oil-repellence.
  • the untreated materials have a kit test grade of zero.
  • oil-repellence of the order of 5/6 5: 200 ml of mixture is composed of 120 ml ricin oil, 40 ml of toluene, 40 ml of N-heptane; 6: 200 ml of mixture is composed of 100 ml of ricin oil, 50 ml of toluene, 50 ml of N-heptane) .
  • grade 1 oil-repellence (1: 200 ml of mixture of ricin oil).
  • An oil- repellent grade of 5/6 was obtained for various types of paper.
  • the applications of the above-mentioned procedure comprise paper and cardboard and fibres used in the paper industry such as, for example, paper for solid or liquid foodstuffs.
  • the applications of said procedure comprise generation of a barrier film on the surface, water- repellent surfaces, or flame-retardant, anti-static, or bio-compatible surfaces.
  • other characteristics may be cited intended for various sectors of use such as waterproofing the paper after colouring, resistance to oxidizing agents, protective coatings, metallizing, improved de-inking by means of modifications to the paper before printing, protecting the product from the action of sunlight and UV radiation, polymerizing with monomers, barrier films for vapours or gases, grafting synthetic polymers onto the cellulose, biodegradable deposits.
  • the methods for obtaining a deposit or grafting are the following taken individually or in any combination: - producing a plasma of the substance which it is wished to deposit (for example see process IV) ;
  • a gas plasma for example, (procedure II) and then causing the substrate to interact with the substance in the gaseous phase, with or without plasma in the same containing chamber;
  • the plasma may at the same time activate the surface during the depositing process (method a) ) , or the depositing step may be preceded by that of activation according to procedure II) and carrying out cyclic processes (method c) ) in which the specimen undergoes plasma activation and immediately or during activation the surface is covered with gas, the molecules of which (for example monomers or radicals) are grafted and/or deposited onto the surface.
  • gas for example monomers or radicals
  • the anti-static properties of the paper or cardboard may be improved by using in particular plasma with metals, or chloromethylsilane, or hydrocarbons such as methane, for example.
  • barrier films to protect the food product from the action of light or UV radiation.
  • Parma ham under the action of sunlight and in the presence of oxygen tends to oxidize some of the aminoacids which contribute to its taste and smell and conversely with a film forming a barrier to radiation and oxygen it is possible to reduce or prevent oxydizing.
  • barrier films are produced for organic substances of various kinds, useful for example in a food package which contains liquid, for example cartons containing fruit juices, wine, milk; these packages must not release organic substances of which they are composed.
  • deposits of organic and inorganic materials on the surface of the paper or cardboard may be obtained with a cold plasma containing acrylates, . vinyl monomers, fluorocarbons, dilanes, siloxanes, organosilanes, saturated hydrocarbons and mixtures of these (method a) ) .
  • acrylates vinyl monomers, fluorocarbons, dilanes, siloxanes, organosilanes, saturated hydrocarbons and mixtures of these (method a) ) .
  • Liquid substances at standard pressure may be used in the gaseous phase under vacuum provided that the vapour tension is of the order of or greater than that of the vacuum chamber.
  • the pressures vary from 0.1 mbar to 20 mbar, more preferably from 0.2 mbar to 5 mbar, still more preferably between 0.3 mbar and 3 mbar.
  • the thicknesses of the layers may be varied: for treatments of a few minutes, deposits of a few tens of nm are produced, while for treatments of some tens of minutes, deposits of more than a micron are produced.
  • Special effects may be produced by creating areas which are hydrophilic to a greater or lesser degree and have varying degrees of affinity to the colour to create designs on the paper, cardboard or metallized areas.
  • the treatments described above may also be obtained with a corona discharge, by means of methods a) b) or c) or d) , at atmospheric pressure which contains mixtures of the gases mentioned above with noble or inert gases or air.
  • a corona discharge by means of methods a) b) or c) or d) , at atmospheric pressure which contains mixtures of the gases mentioned above with noble or inert gases or air.
  • a noble gas or inert gas atmosphere or air it is possible, during (method a) ) or after the corona treatment (method b) or c) ) to cause organosilanes such as hexamethyldisiloxane, in gaseous phase, to flow directly from the electrodes or in areas close to them, onto the surface of the substrate or of the fibres so as to deposit and/or graft it onto them.
  • This last method is important for depositing on and/or grafting onto the surface groups of various types including hydrophobic and hydrophilic groups, and/or groups with properties of affinity for specific substances, and/or with specific properties, for example anti-bacterial, anti-mould, antistatic, flame-retardant, bio-compatible, providing barrier films or films protecting against e/m radiation.
  • deposits conventional and non-conventional, may be applied successively, in the gaseous phase as well as the liquid or solid phase, as for method d) ) .
  • the method of treating paper, cardboard and fibres used in the paper industry comprising the application of plasma to the surface of said paper, cardboard and fibres used in the paper industry according to the invention meets the requirements referred to in the introductory part of this description and at the same time overcomes the disadvantages exhibited by the methods of treatment of the known technology.

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  • Paper (AREA)
  • Laminated Bodies (AREA)

Abstract

L'invention concerne un procédé de travail du papier, du carton et de fibres associées. Elle se rapporte en particulier à un procédé d'amélioration ou d'obtention de manière simple de nouvelles caractéristiques de surface. Ledit procédé consiste à traiter avec un plasma froid la surface des substrats, après ou pendant le dégazage spécifique et approprié.
EP03727948A 2003-05-13 2003-05-13 Procede de traitement au plasma du papier et du carton Withdrawn EP1623072A1 (fr)

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DE102005049290A1 (de) * 2005-06-16 2006-12-28 Siemens Ag Pressenvorrichtung zum Verdichten von Papier und/oder zum Entziehen von Trägerflüssigkeit aus Papier und Verfahren hierzu
BRPI0611762A2 (pt) * 2005-06-16 2010-09-28 Siemens Ag equipamento de peneiração para a produção de papel e processo para o tratamento de fibras não entretecidas
DE102005049231A1 (de) * 2005-06-16 2006-12-28 Siemens Ag Verfahren zur Behandlung eines Prozessgutes bei der Herstellung von Papier, Karton oder Pappe
DE102005049274A1 (de) * 2005-06-16 2006-12-28 Siemens Ag Verfahren zur Behandlung eines Prozessgutes mit großflächigem Plasma
DE102005028024A1 (de) * 2005-06-16 2006-12-28 Siemens Ag Verfahren und Vorrichtung zur Erzeugung großflächiger Atmosphärendruck-Plasmen
DE102005049287A1 (de) * 2005-06-16 2006-12-28 Siemens Ag Siebvorrichtung für die Herstellung von Papier und Verfahren zur Behandlung unverwobener Faserstoffe
DE102006024404A1 (de) 2006-05-24 2007-11-29 Siemens Ag Verfahren zur Verbesserung der Qualität einer Faser-Suspension
PT103951A (pt) * 2008-01-31 2009-07-31 Univ Nova De Lisboa Processamento de elementos eléctricos e/ou electrónicos em substratos de material celulósico
AU2013202841B2 (en) * 2008-04-30 2015-05-07 Xyleco, Inc. Paper products and methods and systems for manufacturing such products
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DE102011088522B4 (de) * 2011-12-14 2014-05-15 Siemens Aktiengesellschaft Steuerung der Blattbildung in einem Papierherstellungsprozess
DE102011090121A1 (de) * 2011-12-29 2013-07-04 Siemens Aktiengesellschaft Ändern einer Formation von Papierfasern in einer Papierbahn
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CN112030602B (zh) * 2020-09-08 2022-03-22 杭州众材科技股份有限公司 一种施胶纸张的脱酸方法
CN114351273B (zh) * 2021-12-02 2023-01-06 华南理工大学 一种基于冷等离子体的纤维素纳米纤维的绿色低能制备方法
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