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
  • D21H17/62—Rosin; Derivatives thereof
• • 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
  • D21H17/66—Salts, e.g. alums
• • 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
  • D21H17/675—Oxides, hydroxides or carbonates

Definitions

• the present invention relates to a process for the sizing of paper with rosin and an aluminium compound in the presence of CaCO3.
• Paper is sized to make it water repellent so that it can be written or printed on with ink without the ink spreading in the paper.
• Sizing usually consists in applying a layer of rosin on the cellu­lose fibers in the paper pulp and this in the presence of an alumi­nium compound that acts as a source of positively charged ions; the presence of these positively charged ions is required, as both the cellulose fibers and the rosin are negatively charged and therefore repulse one another.
• rosin is meant hereabove and hereafter the sizing agent that is obtained from softwood trees.
• rosin is the most widely used sizing material, there are applications where it is not comple­tely satisfactory and where it has been replaced by a group of che­mical compounds, which are best described as "reactive sizes” and often called “synthetic sizes", in contrast to rosin sizes consi­dered to be natural products. Synthetic sizes do not require the presence of an aluminium com­pound. However, their reaction with the fibers in the paper pulp can be relatively slow, compared to the essentially instantaneous interaction between rosin, aluminium compound and fiber. More details about the nature of rosin sizes and synthetic sizes and their use in the paper industry can be found in "Pulp and Paper. Chemistry and Chemical Technology. Third Edition. Volume III", 1981 by James P. Casey (John Wiley & Sons, Inc.), which book is incorporated herein by reference.
• CaCO3 can have been included in different ways into a paper pulp to be sized. It can have been added as filler to in­crease the opacity of the paper. It can also have been added as constituent of paper waste to be recycled and containing CaCO3 as filler or as surface pigment. Moreover, it can have been added partly as filler and partly as constituent of paper waste to be recycled. When CaCO3 comes into the paper pulp as constituent of paper waste to be recycled, the CaCO3-content of the paper pulp can sof course strongly vary in function of the time.
• the aim of the present invention is to provide a process as de­fined before, which avoids the drawbacks of the before-mentioned known process.
• a poly(aluminium hydroxysul­fate) with an OH/Al-ratio of 1-2.5 is used as aluminium compound.
• EP-A-0062015 deals with the sizing of paper with rosin and poly (aluminium hydroxysulfate).
• this document does not disclose the presence of CaCO3 in the pulp to be sized.
• EP-A-0104904 discloses compositions comprising mineral particles, e.g. calcium carbonate, in suspension for use in papermaking (incor­poration of filler in the paper pulp) and in sewage treatment (floc­culation/coagulation). It is recommended to add to said composi­tions a known flocculant such as aluminium sulfate, but only when they are to be used for sewage treatment.
• the OH/Al-ratio of the poly(aluminium hydroxysulfate) should range between 1 and 2.5. If this ratio is less than 1, then there is risk of formation of gypsum and the pH of the pulp can fall below 6. If the ratio exceeds 2.5, then the poly(aluminium hydroxysulfate) is unstable. Very good results are obtained as from an OH/Al-ratio of 1.4. However, results no longer improve when the OH/Al-ratio exceeds 1.6; the process just becomes more expensive as the cost price of the poly(aluminium hydroxysulfate) then increases. Therefore preference is given to an OH/Al-ratio of 1.4-1.6.
• rosin in the process of the invention the different known types of rosin can be used : unsaponified, saponified and cationic.
• the quantity of poly(aluminium hydroxysulfate) to be used depends of course on the quantity of rosin used, which on its turn depends on a number of factors such as the desired degree of sizing, the type and the grinding grade of the raw materials.
• Poly(aluminium hydroxysulfate) for use in the process of the invention can be made according to the processes described in EP-B-0062015 and EP-A-0110846.
• the process of the invention is illustrated by the following example.
• the following starting products are used : - An industrial pulp with a grinding degree of 36°SR and composed of 1/3 pine wood, 1/3 leaf wood, 1/3 CTMP Lijng 230/80 (a semiche­mical and semithermomechanical pulp), 5 % kaolin filler and 2 % Omyalite (trade name for CaCO3); - Dynacoll VS 50, which is the trade name for a saponified rosin size with a solids content of 50 % (a product of Akzo); - An aqueous solution of poly(aluminium hydroxysulfate) with an OH/Al ratio of 1.5 and an Al-content of 1.6 mol/l, which will be called further "PAS".
• the pulp is diluted with water to a solids content of 0.5 %, where­after Dynacoll VS 50, diluted itself to a solids content of 4.25 %, is added thereto in such an amount that 4 g of dry rosin are intro­duced per 100 g of solids contained in the pulp.
• the pulp is then divided into four portions. To the 1 st pulp portion 0.075 ml PAS is added per g of solids contained in said portion, to the 2 nd portion 0.15 ml, to the 3 rd portion 0.225 ml and to the 4th portion 0.30 ml. Then the pH of each pulp is measured, whereafter sheets are made from each pulp.
• the sheets are kept for a week at 23°C and 50 % relative humidity and then subjected to - the Cobb test : g of water absorbed per m2 of paper in 60 sec. - the drop test (DT) : time in minutes required for absorbing a drop of water. - the edge absorption test : height of rise in mm of a coloured liquid, wherein the edge of the sheet is held for 30 minutes. Finally, the pH of the sheets is measured.

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

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Cited By (2)

Citations (2)

• 1989
  • 1989-07-07 BE BE8900745A patent/BE1003749A3/nl not_active IP Right Cessation
• 1990
  • 1990-06-20 EP EP90201613A patent/EP0406932A1/de not_active Withdrawn

Patent Citations (2)

Non-Patent Citations (1)

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