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
  • D21H19/36—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
  • 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
  • D21H21/50—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 form
  • D21H21/52—Additives of definite length or shape

Definitions

• the present invention concerns a procedure for dispersing talc.
• the present invention concerns a procedure with which granulated, finely divided talc can be advantageously dispersed to become a suspension which fulfills the requirements of paper coating paste, at the same time retaining the advantages of granulated talc regarding its handling, and in which standard blunging apparatus can be used.
• Granulating finely ground talc is a method commonly used in order to improve the processability of a bulk-type talc product.
• the moistened talc is compressed with fairly great force into small non-dusting briquettes.
• the talc particles which have been pressed too close to each other and are mutually suitably oriented become combined by action of a van der Waals force like those in the original talc crystal.
• the energy threshold of talc is 4.1 kcal/mol (17.2 kJ/ ol) and the critical distance, 3 A (R.F. GIESE, JR: Interlayer Bonding in Talc and Pyrophyllite, 1974).
• these values are often exceeded, with the consequence that upon granulation the particle size distribution of the suspended talc is coarser than before granulation.
• the pigment In paper coating paste, the pigment must be completely dispersed. Success in this respect implies that the aggregated particles are separated. It is in fact necessary, in suspending finely divided talc, to use especially powerful dispersing agents.
• the energy re ⁇ quirements in the coating talc suspending process are twice those in suspending coating kaolin (J-E, TEIRFOLK, INSKO p. 82-80 VI).
• the viscosity and rheological properties of the suspension to be used in paper coating paste must be stable. No agglomeration or sedimentation must take place, not even during prolonged storage.
• the object of the invention is to provide a procedure in which the use of expensive, high-power special mixers can be avoided.
• the aim of the invention is achieved by a method which is mainly characterized in that the talc is suspended in the presence of at least one hydrophilic mineral substance.
• the talc may be either finely divided powdery talc or granulated talc.
• the original grain size of the granulated finely divided talc is 1-5 urn on the average.
• To the granulating water have been added 0.5-1.5% by weight, of the talc dry weight, e.g. of pH-regulating hydrophilizing and defoaming auxiliary substances, such as e.g. NaOH, polyalkylene glycol and/or its derivatives, and appropriate tensides.
• the above-mentioned auxiliary substances are added at 0.1-0.5% by weight, referred to the total quantity of pigments.
• the temperature In view of — maintaining the effectivity of the additives, the temperature must not rise above 50 C in the suspending operation.
• the hydrophilicity of a mineral is caused by the difference between the surface energy of said mineral and that of the water surface: the smaller this difference, the higher the hydrophilicity of the mineral.
• Talc is by nature strongly hydrophobic.
• the other minerals mentioned are easily wettable.
• a talc/water suspension prepared without auxiliary substances is thixotropic, but it becomes dilata ⁇ t later as the air escapes from the suspension.
• the stability of viscosity is poor, and the rheological properties change with the slow wetting of the talc.
• the viscosity of a suspension with more than 60% dry matter content produced without additives is far too high in view of its use.
• hydrophilic mineral substance the contents of which in the suspension should be 5-90% of the weight of the ultimate suspension, one may use for instance kaolin, calcium carbonate or gypsum suited for paper coating.
• kaolin calcium carbonate
• gypsum a kaolin, calcium carbonate or gypsum suited for paper coating.
• the effect of the mineral substance in dispersing finely divided, granulated talc is based on the following:
• a suspension prepared as described one obtains the original particle size distribution and a high dry matter content: 60-70%, advantageously 65-68%. Complete wetting of the pigments is achieved, and the handling properties of the suspension are good.
• the auxili- ary substances that are used are suited for making a coating paste, and the suspension is stable also in prolonged storage. Dispersing as taught by the invention can be carried out in standard blungers, and the processability advantages afforded by the talc granulation can be preserved.
• the ultimate dry matter content of the suspension was 65%, thereof 50% talc and 50% kaolin. The suspension process took place in a Kady Mill apparatus.
• the sus ⁇ pension had a viscosity of 100 mPas/50 r/min.
• the viscosity and rheological properties did not change during storage for 24 hours.
• the suspension was used to coat LWC paper, with good results.
• the ultimate dry matter con ⁇ tent of the suspension was 60.0%, thereof 50% talc and 50% kaolin.
• the suspension process took place in the laboratory with a Diaf apparatus.
• the viscosity of the suspension was 75 mPas/20 r/min. The viscosity and rheological properties did not change in 24-hr storage.
• the suspension had viscosity 80 mPas/20 r/min.
• the viscosity and the rheological properties changed substantially during storage for 24 hrs.
• the sus ⁇ pension was unstable.
• Fine-grained granulated talc with 2.5 ⁇ m average grain size was dispersed in a suspension prepared of calcium carbonate with 1.7 urn average grain size, to the suspension water of which had been added, among others, 1.2 % polyalkylene glycol (Pluriol PE 6400) at 1.2% by weight, and sodium hydroxide at 0.02% by weight of the talc- dry weight. Dispersion was carried out in the laboratory with a Diaf apparatus. The ultimate dry matter content of the suspension was 60%.
• the grain size of the dry matter of the suspension with different carbonate/talc proportions was as follows:
• Fine-grained granulated talc with average grain size 2.2 urn was dispersed with a Diaf apparatus in a suspension prepared of gypsum (CoCoat ) meant for paper coating, to the suspension water of which was added polyethylene glycol (Pluriol 6400) 0.8% by weight and sodium hydroxide 0.02% by weight, of the weight of talc.
• the ultimate solid matter content of the suspension was about 60%.
• the ultimate dry matter content of the suspension was about 64% and it contained 70-95% talc and 30-5% kaolin.
• Suspension was carried out in the laboratory with a Diaf apparatus. The viscosity and rheological properties did not change at storage for 24 hrs. The viscosity at different mixing proportions was:

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• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Paper (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)

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Publications (2)

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Family Applications (1)

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• 1984
  • 1984-03-30 FI FI841298A patent/FI70805B/fi not_active Application Discontinuation
• 1985
  • 1985-03-28 DE DE8585901454T patent/DE3571399D1/de not_active Expired
  • 1985-03-28 EP EP85901454A patent/EP0186665B1/de not_active Expired
  • 1985-03-28 WO PCT/FI1985/000030 patent/WO1985004344A1/en not_active Ceased
  • 1985-03-29 IT IT20153/85A patent/IT1200440B/it active
  • 1985-03-29 CA CA000477926A patent/CA1247493A/en not_active Expired

Non-Patent Citations (1)

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