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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
• • 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
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/10—Phosphorus-containing compounds
• • 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
  • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
• • 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
• • 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
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent

Definitions

• the present invention relates to stable, concentrated aqueous gypsum suspensions that are useful for the production of paper and cardboard and contain high amounts of gypsum.
• stable, concentrated aqueous gypsum suspensions we mean suspensions having a CaSO 4 *2H 2 O concentration comprised between 60% and 85% by weight.
• European patent EP 0056200 B1 a method was described allowing the use of aqueous calcium sulphate suspensions, which are directly prepared in a reactor located next to the paper production plant and introduced in diluted form (generally with concentration below 20%) directly in the paper production plant.
• This method has a drawback: it also needs the preparation, directly next to the paper production plant, of the aqueous suspension of calcium sulphate, because it is economically disadvantageous to transport the large amounts of water of such suspensions.
• the Applicant has now found that it is possible to use stable, concentrated aqueous suspensions of gypsum in the production of paper.
• a stable aqueous gypsum suspension having Brookfield viscosity at 25°C and 100 rpm comprised between 100 and 1,000 mPa*s and containing from 60 to 85% by weight of gypsum in the form of calcium sulphate dihydrate (Ca 2 SO 4 .2H 2 O) is added to the cellulose aqueous suspension used for the production of paper.
• said stable, aqueous gypsum suspension which represents a further object of the present invention, contains from 0.1 to 2% by weight of an acrylic sulphonated polymer, or of an acrylic carboxylated polymer or of a polynaphthalene sulphonate, and from 0.1 to 1 % by weight of an organic polyphosphonate, and comprises gypsum in dihydrate form having particle size between 35% and 60% below 2 micron.
• an acrylic sulphonated polymer or of an acrylic carboxylated polymer or of a polynaphthalene sulphonate, acting as dispersing agent, and of the organic polyphosphonate allows to obtain stable, concentrated gypsum suspensions having rheological characteristics and stability which render them suitable for use in the method according to the invention.
• polynaphthalene sulphonate is preferred, because, advantageously, it can also be used in acid environments, that are typical of the paper production with acidic sizing, that is at pH about 4.5.
• the Brookfield viscosity of the suspensions is comprised between 100 and 500 mPa*s.
• the acrylic sulphonated polymers useful for the preparation of the suspensions of the present invention are obtained by polymerisation of acrylic and/or methacrylic acid, in acidic or salt form, with a monomer containing a sulphonic functional group and have a molecular weight from 5,000 to 40,000 dalton (measured with an acrylic acid standard); they are well known polymers, available on the market, and sold by way of example in the form of aqueous slurries by Lamberti SpA; they can be used in this form for the preparation of the gypsum suspensions of the invention.
• the molar ratio between the total sum of acrylic and/or methacrylic acid and monomer containing a strongly acidic functional group is from 3 to 30, preferably from 3 to 10.
• the sulphonated acrylic polymer is a copolymer of acrylic acid, methacrylic acid and 2-acrylamido-2-methyl-1-propanesulphonic acid, where the molar ratio between acrylic and methacrylic acid is from 2 to 8.
• the polynaphthalene sulphonates useful for the realisation of the present invention are condensation products of formaldehyde and sulphonated aromatics acting as dispersants, and are also normally available in the market; they are generally prepared by reacting an aromatic sulphonated compound (such as naphthalene sulphonic acids, naphthol sulphonic acids, alkylated naphthalene sulphonic acids, alkylated naphthol sulphonic acids, and also toluenesulphonic acid, benzenesulphonic acid, phenolsulphonic acid and similar compounds) with formaldehyde, to form a condensation product which is usually neutralised or alkalinised by adding a sodium hydroxide solution.
• an aromatic sulphonated compound such as naphthalene sulphonic acids, naphthol sulphonic acids, alkylated naphthalene sulphonic acids, alkylated naphthol sulphonic acids, and also to
• organic polyphosphonate we mean organic phosphonates containing two or more phosphonic groups, in the form of acid or salt thereof.
• Polyphosphonates useful for the realisation of the present invention are: aminotri(methylene-phosphonic acid), aminotri(methylene-phosphonic acid)pentasodium salt, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt, diethylenetriamine penta(methylene phosphonic acid)pentasodium salt, diethylenetriamine penta(methylene phosphonic acid)trisodium salt, hexamethylene diamine tetra(methylene phosphonic acid), hexamethylene diamine tetra(methylene phosphonic acid)potassium salt, and mixtures thereof.
• aqueous gypsum suspensions of the present invention are repared by adding hemi-hydrate gypsum to an aqueous solution containing the dispersing agents and the organic polyphosphonate in a bead mill, gently grinding to homogenise the suspension.
• the dihydrate gypsum which is obtained in these conditions has a particle size from 35% to 60% by weight below 2 microns.
• the grinding avoids excessive sedimentation and compaction of the product, even in case no suspending agents are used.
• the hemi-hydrate gypsum useful for the preparation of the aqueous suspensions of the present invention is commercially available and is normally obtained by calcinating dihydrate gypsum.
• the bead mill is charged with 400.6 g of water, 6.9 g of Sequion 50 K33 and 8.2 g of Tamol NN 0104.
• Two series of sheets are prepared having different fillers, the first with calcium sulphate dihydrate prepared as sample No. 1 of Example 1, the second with calcium sulphate dihydrate prepared according to the method of patent EP 0056200 B1 .
• the paste is then inserted in the sheet-maker machine and the sheet is prepared.
• the 2 nd series is prepared in the same conditions.
• the sheets are conditioned for 24 hours in a room at 21°C and 50 % r.h.
• the charge is calculated by multiplying the ash value at 500°C per 1.25 (conversion factor from CaSO 4 to CaSO 4 *2H 2 O).

Landscapes

• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=39638678

Family Applications (1)

Country Status (2)

Citations (9)

• 2007
  • 2007-02-16 IT ITVA20070018 patent/ITVA20070018A1/it unknown
• 2008
  • 2008-01-16 EP EP08100527A patent/EP1967649A1/de not_active Withdrawn

Patent Citations (9)

Also Published As

Similar Documents

Legal Events