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WO1990001581A1 - Procede pour la fabrication de papier photostable a partir de pate mecanique, et papier produit selon ce procede - Google Patents

Procede pour la fabrication de papier photostable a partir de pate mecanique, et papier produit selon ce procede Download PDF

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Publication number
WO1990001581A1
WO1990001581A1 PCT/SE1989/000419 SE8900419W WO9001581A1 WO 1990001581 A1 WO1990001581 A1 WO 1990001581A1 SE 8900419 W SE8900419 W SE 8900419W WO 9001581 A1 WO9001581 A1 WO 9001581A1
Authority
WO
WIPO (PCT)
Prior art keywords
paper
coating
pigment
light
paper web
Prior art date
Application number
PCT/SE1989/000419
Other languages
English (en)
Inventor
Günther Peters
Original Assignee
Lumalampan Aktiebolag
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 Lumalampan Aktiebolag filed Critical Lumalampan Aktiebolag
Publication of WO1990001581A1 publication Critical patent/WO1990001581A1/fr

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
    • D21H19/00—Coated paper; Coating material
    • D21H19/80—Paper comprising more than one coating
    • D21H19/82—Paper comprising more than one coating superposed
    • D21H19/822—Paper comprising more than one coating superposed two superposed coatings, both being pigmented
    • 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
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/38—Coatings with pigments characterised by the pigments
    • D21H19/385—Oxides, hydroxides or carbonates
    • 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
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/38—Coatings with pigments characterised by the pigments
    • D21H19/40—Coatings with pigments characterised by the pigments siliceous, e.g. clays
    • 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
    • D21H19/00—Coated paper; Coating material
    • D21H19/80—Paper comprising more than one coating
    • D21H19/84—Paper comprising more than one coating on both sides of the substrate
    • 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
    • D21H21/30—Luminescent or fluorescent substances, e.g. for optical bleaching

Definitions

  • the present invention relates to a method for improving the light-stability of paper, preferably paper produced from lignin-rich mechanical or thermomechanical pulps, so-called high yield pulps, and to paper produced in accordance with the method.
  • lignin compounds which contained ring-con- jugated alpha carbonyl bonds, alpha-beta-olefin bonds or biphenyl bonds are sensitive to light-induced chemical reactions, resulting in yellow reaction products.
  • those lignin structures whose side chains are saturated are resistant to radiation down to a wavelength of 300 nanometers.
  • Paper is normally surface treated with a coating com ⁇ position containing a filler (often kaolin), a binder and various additives (auxiliary chemicals) .
  • a filler often kaolin
  • auxiliary chemicals various additives
  • Coating substances or formulations are applied to paper in order to modify its surface properties, such as brightness, opacity, printability, mechanical strength, the paper's water retention, .etc.
  • the coating can be applied with the aid of rolls in a so-called paper coating section, or with the aid of doctors against special abutment rolls, or against drying cylinders in a fourdrinier machine.
  • a coating formu ⁇ lation may also contain an emulsifier, polysaccharides, dispersing agents, UV-absorbents, optical bleaches, foam retarders, fungicides, etc., as described in
  • Other coating formula ⁇ tions are described in EP-A1-0015517, SE-B-.350083, SE-B-353358 and SE-B-7908927-2. The latter three experts ⁇ cations relate primarily to grain size distribution.
  • the filler incorporated in such coating formulations must also be considered to constitute a contaminant.
  • the binders used in the present context have relatively low vapour pres ⁇ sures at the working temperatures which prevail during paper manufacturing processes, the fact that binder vapours are present in the working environment of a paper mill cannot be ignored.
  • fillers pigments
  • recycled paper constitutes the starting material for paperboard and for interlayers or for fluting, where, for instance, clay may be preferred
  • the filler will create disrup- tions in other uses of the paper fibres.
  • the clay present can be held suspended to a large extent in the paper pulp, and therewith be prevented from forming deposits in the board or paper sheets produced, the clay will nevertheless create wear on pumps and valves in particular, during passage of the pulp to the paper machine.
  • the coating formulation constitutes up to 20% of the weight of the recycled paper, which creates problems unless other recycled fibres are available for admixture with thinning of the pulp.
  • the buffer volume of pulp sheets is the only auxiliary means for thinning out the coating for ⁇ mulation, if a given batch of recycled material has a high coated paper content.
  • the object of the present invention is to provide a paper of sufficient quality for archival use and having good print contrast made from relatively inexpensive starting material.
  • the invention effectively reduces the load on the environment of hitherto used coating chemi ⁇ cals, which are mainly imported to paper producing countries.
  • archival use is meant that the paper shall not sub ⁇ sequently yellow or be changed in any other way such as to reduce the contrast between paper and the text prin- ted thereon or any other form of print or writing there ⁇ on, either when the paper is stored in a dark environ ⁇ ment or when the paper is exposed to natural or artifi ⁇ cial light.
  • paper used in office copying machines is subjected to a relatively large quantity of luminous energy (light) therein. This light has a wavelength composition which ensures rapid transfer of text and images, but which is unkind to the paper fibres.
  • the desire which the invention is intended to fulfill is primarily is one of providing a paper which, over the passage of time, will remain white, as .far as can be discerned by the human eye.
  • the natural tendency of the paper fibres to yellow is inhibited in all instances, and the paper surfaces will reflect light within the desired wavelength range.
  • the paper is treated in accordance with a method which, subsequent to speci- fic chemical processing of the pulp against
  • Coating 1 (nearest the surface of the paper), designated the protective layer, comprising an inorganic pigment which is both UV-refle ⁇ tive and UV-absorptive,
  • Coating 2 (external of layer 1) forming an outer layer having maximum brightness and comprises an optical bleach (whitening. substance/brightener) and inorganic filler.
  • Coating 1 which is applied directly onto the paper, is intended to protect the UV-sensitive compounds of the paper, so as to avoid undesirable photolytic reactions between energy-rich UV-radiation and, e.g., lignin structures containing ring-conjugated alpha-carbonyl- bonds, alpha-beta-olefin-bonds or biphenyl-bonds.
  • the protective layer is applied in the form of a thin coating comprising a pigment mixture, binder, dispersing agent and water.
  • the pigment mixture may comprise the following substances: a/ highly pure titanium dioxide (Ti0 2 ) having a grain size of 0.1-1.0 micron (preferably 0.3-0.6 micron)
  • a/ functions as an UV-absorber, b/ and c/ function as UV-reflectors.
  • the mixing ratio calculated in parts by weight is
  • the coating weight, or grammage is 0.2-0.8 g/m (pref-
  • Usable binders include , styrene-acrylate latex, methyl cellulose or PEO (polyethylene oxide).
  • the preferred dispersing agent is TU (nonyl-phenol- ethylene-oxide) .
  • the protective coating suspension is produced from: 10 kg pigment mixture (Ti0 2 + BaS0 4 + Si0 2 ) 10-20 kg binder 0.1-0.2 kg dispersing agent 985 kg (max) water, which may have a hardness of max 3 dH and an iron content of max 0.02 ppm.
  • This protective coating suspension can be used on dry paper (less than 7% moisture).
  • the suspension is prepa ⁇ red with the aid of dispersing apparatus and is held under agitation, or stirring, until it is used for application on the paper web, preferably by spraying on dry paper.
  • the protective coating, or layer When the protective coating, or layer, is applied in a paper machine, when the paper web has reached a dryness of between 65 and 75%, the water content of the suspen ⁇ sion is lowered beneath 900 kg when spraying and still lower when stroking or rolling the coating suspension on the paper.
  • Coating 2 f is applied on top of the protective coating and comprises one or more white pigments, the whiteness of which is further amplified by adding one or more optical bleaches.
  • the white pigment may comprise pure qualities of titanium dioxide, barium sulphate, calcium carbonate or aluminium silicate having a grain size smaller than 1.0 micron.
  • One of the aforesaid substances, or a mixture of several of said substances, can be used in the pigment coating, depending on the final use of the paper.
  • the optical bleach used com ⁇ prises one or more moisture-resistant, fluorescent, inorganic materials, so-called luminescent materials.
  • Substances which can be used to particular advantage in this context are blue-reflecting substances such as strontium pyrophosphates (Sr 2 P 2 0 7 :Eu) or zinc sulphide (ZnS:Ag).
  • the paper can be toned blue, by increasing the quantities of these substances. If a pink-reflecting paper surface is desired, yttrium oxide (Y 2 0_:Eu) or magnesium fluorogermanate can be used. Barium- agnesium- aluminate and zinc-cadmium sulphide will provide a green-toned paper.
  • Figure 1 illustrates excitation and reflection spectra for a blue-colour producing luminescent material (optical bleach), namely zinc sulphide
  • Figure 2 illustrates a corresponding emission spectrum.
  • luminescent materials refers to powder-form, inorganic materials which are special chemical compounds having pronounced luminescence in a crystalline state, achieved subsequent to subjecting the materials to a separate annealing process. Light is generated by these substances as a result of the coaction of large groups of atoms or molecules, at times whole crystals, which are subjects for excitation energy absorption.
  • Inorganic luminescent materials do not constitute ideal crystals, but have the form of true or actual crystals with lattice disruptions. The energy level forms in these true crystals have the greatest significance in the production of luminescence.
  • the production of the luminescent materials is charac ⁇ terized by reactions in solid phase, which normally produce non-stoichiometric compositions of the basic material and additives of special doping substances, so- called activators.
  • activator centers are created in the form of dispersed activator ions, or ion groups, which are later responsible for the emission of light.
  • the luminescent materials can be excited by different types of radiation and emit light within different wave ⁇ length bands.
  • the exciting radiation is often UV- radiation (ultra violet), or at times also short-wave, visible radiation.
  • Certain luminescent substances may require excitation by photons -of higher energy content, for instance X-ray radiation.
  • the luminescent material In order for a fluorescent material to be suitable for use as an optical bleach (whitening agent) in a paper coating formulation, the luminescent material must possess the following properties:
  • the excitation spectrum must lie within the wave length range of 350-420 nm in order for the luminescent material to be excited by incident light.
  • the emission spectrum must lie within the wave length range of 400-500 nm, preferably 430-470 nm, with a maximum spectral bandwidth of 40 nm ("blue emitter").
  • the luminescent material must be light-stable against incident radiation and long-term resistant against moisture and other components present in the coating formulation. 4.
  • the maximum grain size distribution of the lumi ⁇ nescent material shall lie between 1 and 5 micron, preferably between 1 and 3 micron.
  • Luminescent materials which fulfill these requirements satisfactorily include particular luminescent powder types of magnesium tungsten (MgW0 4 :W) and zinc sulphide (ZnS:Ag) or (ZnS:Ag + CoO.Al-O-).
  • the substances can be used advantageously in mixture, depen- ding on the intended use of the paper.
  • Binders which can be used in the pigment coating include styrene acrylate latex, polyethylene oxide or some other water-soluble binder capable of imparting to the paper properties which are favourable for given areas of use, particularly with respect to reflected light.
  • the binder and white pigment may not have strong absorption fre ⁇ quencies within the spectral range of 280-400 nm capable of disturbing excitation of the activator centra of the optical bleach.
  • the respective refraction indexes of the white pigment and the binder should differ from each other as far as possible, so as to obtain maximum coverage ability.
  • the coverage ability of the pigment coating is directly proportional to the relative refraction index. This is defined by the for ⁇ mula n P
  • n pigment refraction index for surrounding medium (binder) .
  • the surrounding medium (m) may comprise other additives (filler, extender) which are optically less active than the pigment. This implies a lower refraction index, accompanied by a higher value of the relative refraction index.
  • the coating formulation (coating 2) should comprise fine-grain pigment and optionally extender, i.e. pigment and extender having a grain size beneath 1.0 micron. This fine grain size will amplify remission in the blue wavelength range in comparison with remission in the yellow wavelength range. Since remission is the diffuse reflection of incident light, the eye will discern the remitted light as the colour possessed by the surface viewed. This is primarily due to the fact that the remission comprises non-parallel radiation. The colour impression obtained from the paper surface in question will remain the same, irrespective of the angle from which the paper is viewed, i.e. irrespective of the reflection angle of the incident light.
  • the remission will increase with decreasing wave- length.
  • the remission is greater for blue light than for red light, measured at a constant grain size of the pigment present in the surface of the paper.
  • the paper will therefore whiten with time, since the wood fibres lying beneath the protective coating will yellow slight- ly, despite the presence of said coating, and therewith complement the initial blue tone.
  • the mixture of UV- absorptive and UV-reflective substances in the protec ⁇ tive layer determine the balance points, inasmuch as these can be selected such that the reflected wave length of 185 nm is dominant. UV-light of this wave length is much richer in energy than yellow light, and upon remission is able to extinguish part of the yellow remission.
  • compositions comprising four mutually different compositions have been tested, these compositions being:
  • optical bleach (whitening agent) MgW0 4 : W
  • styrene-acrylate latex (binder) 0.1 kg surfactant 32.98 kg water, max 3 dH° ; iron content, max 0.02 ppm
  • optical bleach (whitening agent) MgW0 4 : W
  • styrene-acrylate latex 0.1 kg surfactant 32.9 kg water , max 3 dH o; iron c ° ntent max °- 02 PP m
  • optical bleach (whitening agent) ZnS:Ag
  • styrene-acrylate latex 2.0 kg optical bleach (whitening agent) (ZnS:Ag) 5.0 kg styrene-acrylate latex
  • coating 2 2.0 g/m
  • coating 2 1.5 g / V
  • the inventive method can be practised in two ways.
  • the protective coating is sprayed onto the paper web in a paper machine when said web has a dry solids content of between 65 and 70%.
  • the paper is then dried in an intermediate step to a dry solids content of between 80 and 90%, whereafter the pigment coating is applied to both sides of the paper web, with the aid of a coating applicator or a doctor blade.
  • the paper is delivered from a paper machine to a separate coating machine, in which the protective coating is applied, either by spraying or with the aid of a doctor blade.
  • the protective coating is then dried and the pigment coating subsequently applied, either with the aid of rolls or with the aid of doctor blades.
  • the coated paper is then finally dried, prior to being rolled-up or cut into lengths.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Paper (AREA)

Abstract

Est décrit un procédé dans lequel du papier fini machine ou du papier en cours de fabrication dans un fourdrinier par exemple, est enduit sur les deux faces d'un revêtement protecteur renfermant des matières ou des substances qui vont réfléchir la lumière ultraviolette et également absorber cette lumière. Le revêtement protecteur présente sur le dessus un revêtement pigmentaire contenant des substances luminescentes, de sorte que la lumière renvoyée va posséder une composition de longueur d'onde telle que l'÷il humain va discerner le papier comme étant de préférence blanc.
PCT/SE1989/000419 1988-08-05 1989-07-25 Procede pour la fabrication de papier photostable a partir de pate mecanique, et papier produit selon ce procede WO1990001581A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8802836-0 1988-08-05
SE8802836A SE461596B (sv) 1988-08-05 1988-08-05 Foerfarande foer tillverkning av ljusstabilt papper samt papper erhaallet genom foerfarandet

Publications (1)

Publication Number Publication Date
WO1990001581A1 true WO1990001581A1 (fr) 1990-02-22

Family

ID=20373034

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1989/000419 WO1990001581A1 (fr) 1988-08-05 1989-07-25 Procede pour la fabrication de papier photostable a partir de pate mecanique, et papier produit selon ce procede

Country Status (5)

Country Link
AU (1) AU3987489A (fr)
ES (1) ES2015767A6 (fr)
PT (1) PT91335B (fr)
SE (1) SE461596B (fr)
WO (1) WO1990001581A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021891A1 (fr) * 1999-09-23 2001-03-29 Stora Enso Publication Paper Ag Papier d'impression couche, optiquement blanchi, et procede de fabrication de ce papier
EP1126081A3 (fr) * 2000-02-18 2003-04-16 Felix Schoeller jr Foto- und Spezialpapiere GmbH & Co. KG Support pour couches d'enregistrement
WO2005095709A1 (fr) * 2004-03-23 2005-10-13 Imerys Pigments, Inc. Blanchiment reducteur efficace de pates minerales

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE310599B (fr) * 1965-08-24 1969-05-05 Time Inc

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE310599B (fr) * 1965-08-24 1969-05-05 Time Inc

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001021891A1 (fr) * 1999-09-23 2001-03-29 Stora Enso Publication Paper Ag Papier d'impression couche, optiquement blanchi, et procede de fabrication de ce papier
US6773549B1 (en) 1999-09-23 2004-08-10 Stora Enso Publication Paper Gmbh & Co., Kg Method for producing an enameled, optically brightened printing paper
EP1126081A3 (fr) * 2000-02-18 2003-04-16 Felix Schoeller jr Foto- und Spezialpapiere GmbH & Co. KG Support pour couches d'enregistrement
US7014893B2 (en) 2000-02-18 2006-03-21 Felix Schoeller Jr. Foto-Und Spezialpapiere Gmbh & Co. Kg Support material for recording layers
WO2005095709A1 (fr) * 2004-03-23 2005-10-13 Imerys Pigments, Inc. Blanchiment reducteur efficace de pates minerales
US7648032B2 (en) 2004-03-23 2010-01-19 Imerys Pigments, Inc. Effective reductive bleaching of mineral slurries

Also Published As

Publication number Publication date
ES2015767A6 (es) 1990-09-01
SE8802836D0 (sv) 1988-08-05
PT91335A (pt) 1990-03-08
SE461596B (sv) 1990-03-05
AU3987489A (en) 1990-03-05
SE8802836L (sv) 1990-02-06
PT91335B (pt) 1995-06-30

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