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
  • D21H17/20—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
  • D21H17/375—Poly(meth)acrylamide
• • 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
  • D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
• • 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
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect
  • D21H23/765—Addition of all compounds to the pulp

Definitions

• This invention can be used to improve the retention of fillers during papermaking, to prevent a harmful agglomera- tion of filler particles in paper and to obtain a uniform distribution of filler in paper.
• the invention also miti ⁇ gates the harmful effect of filler on the strength of paper as well as the harmful effect of retention aids on paper formation. Aggregates of filler particles and fines from beaten or refined pulps contribute to a high opacity in the paper.
• Purpose of the invention The purpose of this invention is to achieve an improved filler retention without generation of dense filler agglome ⁇ rates.
• a solution to this problem has been found to be to
• the fines have an ability to scatter light and thereby im- prove the opacity of the paper provided only that a distance of at least one half wave length of the light can be main ⁇ tained between the fibrils in the paper, something that will be promoted by coflocculation of fines and fillers.
• the fibrils have a certain stiffness, so that the surface tension will not give too much optical contact between them during drying of the paper.
• the fibrils should, therefore, preferably derive .from mechanical or chemimechanical pulp, in which the fibre wall, from which the fibrils have been peeled off, still retains the stiffness of wood.
• the pulp should preferably be peroxide bleached, since this invention will be used mainly-'in combination with manufacture of printing paper requiring a high brightness.
• part of the main furnish can be subjected to a separate refining process producing a suitable fine grade pulp.
• the quantity required amounts to 20% on the weight of the filler added.
• the re ⁇ fining should take place at a consistency of 20-50% in order to produce fibrils and lamellas rather than broken fibres.
• the fine grade pulp which conveniently can be a commer ⁇ cial mechanical pulp of very low freeness, for example 50 ml C.S.F., is diluted in an agitated tank preferably with white water from the first part of the drainage table to a con ⁇ sistency of conveniently 5-10 g/1.
• the pulp is then mixed with a filler suspension at a rate giving for example 20% fines on the weight of the filler, which is conveniently achieved by continuous pumping of the two suspensions into a mixing chamber.
• a retention aid is introduced for coflocculation of fines and filler.
• the floe suspension is then pumped into.the furnish for example ahead of the fan pump feeding the paper machine.
• Fig. 1 shows a SEM micrograph of a sheet made from the fines fraction of a mechanical pulp.
• the black bar at the bottom of the picture is 20 microns.
• Fig. 2 shows a SEM micrograph of a sheet made from equal parts of fines and filler.
• the black bar at the bottom of the picture is 20 microns.
• Fig. 3 shows filler distribution through the thickness of two sheets made from coflocculated blends of equal parts of fines and mineral filler.
• Fig. 4 shows filler retention in a sheet mould as a function of retention aid additon.
• Fig. 1 shows a SEM micrograph of a mechanical pulp of the required quality.
• the black band at the bottom is 20 microns long, while an ordinary spruce fibre is 30 microns wide.
• Fig. 2 shows a micrograph of a sheet made from equal- parts of such fines and a filler. It is seen that this sheet has a more uniform but still porous structure, the pore volume being 65%.
• the floes of fines and filler mentioned in this invention, should in the paper have the same structure as in this sheet thereby contributing to the opacity of the paper.
• Fig. 3 shows the filler distribution from top side to wire side in two sheets made from equal part of filler and fines flocculated by a polymer. The picture demonstrates that the filler particles in these sheets were so firmly bound to the fines that they retained their positions in the sheet during drainage, pressing and drying.
• Fig. 4 shows the results of retention studies on a labo ⁇ ratory sheet mould, in which sheets have been made either after addition of filler and retention aid to the furnish (P+P) or after addition of preflocculated fines-filler aggregates to the sheet machine. (P+F) It is seen that a polymer consumption of 150 g/t during conventional sheet-making gave the same retention as a polymer consump- tion of 60 g/t during coflocculation of fines and filler.
• SUBSTITUTE SHEET can be explained by a very much better formation and by less interference of the filler particles with fiber-fiber bond ⁇ ing. It is remarkable that this strength increase could be combined with a reduction of the density and an increase of the light scattering. Normally, the latter two properties will deteriorate, when strength goes up. It should be obser ⁇ ved that the positive effects of coflocculation are obtained without any extra expenses for chemicals or pulp.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=20358763

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (1)

Citations (4)

Family Cites Families (1)

• 1985
  • 1985-01-15 SE SE8500162A patent/SE455318B/sv not_active IP Right Cessation
  • 1985-12-10 DE DE19853590715 patent/DE3590715T1/de active Pending
  • 1985-12-10 GB GB08622077A patent/GB2181464B/en not_active Expired
  • 1985-12-10 WO PCT/SE1985/000514 patent/WO1986004370A1/en active IP Right Grant
  • 1985-12-10 DE DE19853590715 patent/DE3590715C2/de not_active Expired - Fee Related
  • 1985-12-10 EP EP19860900327 patent/EP0209538B1/en not_active Expired - Lifetime
• 1986
  • 1986-09-11 FI FI863682A patent/FI80742C/fi not_active IP Right Cessation

Patent Citations (4)

Non-Patent Citations (6)

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