Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
  • D21B1/14—Disintegrating in mills

Definitions

• This invention relates to a method of making mechanical, thermo echanical and chemi-mechanical pulp of ligno-cell- ulose containing material, such as softwood, hardwood or bamboo, with the puppose of being used in different paper and cardboard qualities etc.
• the material is chipped to chips, which are refined to pulp, normally in a disc-refiner in one, two or sometimes three steps.
• Different types of pulp made according to this method normally are distinguished, viz. PIMP (refiner mechanical pulp), TMP (thermomechanical pulp), CMP (chemi-mechanical pulp) and CTMP (chemi-thermomechanic ⁇ al pulp), as listed below.
• the pulps have a high content of long fibres and good streng properties.
• the energy consumption is high, about 2000 kWh/ton pulp. Owing to the high content of long, stiff fibres, the forming in the paper aking machine and the smoothness and optical properties of the paper at times can be unsatisfactory.
• blocks i.e. logs cut to a definite length
• Variants corresponding to those listed above are as follows. Groundwood grinding of untreated wood at atmospheric pressure
• Groundwood pulps have a lower content of long fibres than refined pulps. For this reason, the strength properties are inferior, but forming, smoothness and optical properties are better than at refining. The energy consumption is considerably lower, about 1000 kWh/ton pulp.
• One serious disadvantage is that roundtimberhas to be used.
• Chemiground ood has good strength properties. Its disad ⁇ vantage, however, is that the heart of the log is not im ⁇ pregnated. The heart, therefore, remains dark at digestion, thereby reducing the ISO-brightness of the pulp and render ⁇ ing the pulp difficult to bleach. The method, therefore, among other reasons has not got a wide-spread use.
• the present invention has the object to provide a method, which eliminates the disadvantages of high energy consumption and of inferior strength and dependency on round timber at grinding.
• the raw material enters the process at 1.
• the raw material can be in the form of logs, small pulpwood, slabs, edgings or other piece shape having the minimum length stated below.
• the raw material is washed clean at 2 by heavy water sprays which remove sand and other impurities.
• the raw material then is cross-cut at 3 » for example by cross-cutting saws, to lengths adapted for the defibering apparatus under 8 below.
• the minimum length in question is 200 mm, but pref ⁇ erably at least 500 mm.
• the cross-cut wood is cleaved at 4 to sticks, which have a minimum dimension across the fibre direction of at maximum 50 mm, preferably at maximum 25 mm.
• the sticks thus, can have the form of ribs with a width, which may be of the same size as the dimension of the raw material in transverse direction, but the thickness of which does not exceed the dimension stated.
• the cleaving can be carried out by cleaving apparatuses of different type preferably of the type cleaving the wood along its fibre structure, so that the fibres to the greatest possible exten remain intact.
• the object of the cleaving is to facilitate the subsequent impregnation.
• the raw material for example, consists of thin slabs or edgings
• the cleaving of course, can be passed over.
• the sticks then are steamed at 5 with steam of atmospheric pressure or low pressure for removing the air, which impedes the impregnation.
• the sticks then are impregnated at 6 with liquid, which may be water, possibly containing chemicals.
• the liquid is pressed into the fibre material by means of a high hydraulic pump pressure.
• the chemicals may be bases, such as caustic soda, salts of alkali metals, for example sodium sulphite or sodium bi ⁇ sulphite or percompounds, for example peroxide. Mixtures of, for example, caustic soda and sodium sulphite or per ⁇ oxide may also be used.
• the impregnation also can be carried out in two or more steps with different chemicals, ⁇ in which case the excess or spent chemicals are removed between the steps.
• the impregnated sticks react at 7 with the chemicals for a certain time and at a certain temperature.
• the reaction can take place at atmospheric pressure or:.overpressure and in liquid phase or steam phase.
• excess liquid is drained, and the sticks are defibered at 8, in such a manner, that the sticks, with the fibres oriented in a definite direction, are pressed against the surface of a rotating defibering device, while water is being supplied.
• the fibres thereby shall be oriented in the same plane as the tangent press surface, and the direction of movement of the surface preferably shall be perpendicular to the fibre direction.
• Normal grind ⁇ ers possibly pressurized, can be used, comprising a grind ⁇ stone built-up of sharp, hard grains, for example of alumin ⁇ ium oxide or silicon carbide, held together by a ceramic binder.
• the grinder and its feed means must be adapted for the treatment of sticks instead of blocks.
• existing pressing devices chains, screws and the like are less suitable.
• Devices of pocket type are to be preferred, at which the wood is pressed against the grinding surface by a pressing plate. After defibering, the pulp produced is removed at 9 for continued processing, such as screening, possibly washing, bleaching etc.
• the cross-cutting at 3 can be made so that the resulting lengths are twice or several times longer than the final lengths adapted for the defibering apparatus, and the finishing cross-cut is made before the ldefibering.
• the steaming at 5 can be passed over or replaced, for example, by vacuum evacuation.
• the reaction at 7 can be left out.
• Other types of defibering apparatuses can be used.
• the defibering for example, can be carried out against the plane surface of a defibering disc.
• the de ⁇ fibering surface can be built-up of other materials, for example steel and cemented carbide.
• Pulp types corresponding to the different refiner and groundwood pulps according to above can be manufactured of the sticks in the way as follows.
• Mechanical pulp possibly steaming, impregnation with water, defibering at atmospheric press ⁇ ure
• Chemithermo- steaming, impregnation with chemicals, mechanical pulp possibly d i ges tion, d efibering at steam pressure possibly d i ges tion, d efibering at steam pressure.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Reinforced Plastic Materials (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 1986
  • 1986-11-06 SE SE8604769A patent/SE458690B/sv not_active IP Right Cessation
• 1987
  • 1987-10-27 EP EP19870907450 patent/EP0329694A1/en not_active Withdrawn
  • 1987-10-27 WO PCT/SE1987/000498 patent/WO1988003581A1/en not_active Application Discontinuation
  • 1987-10-27 JP JP50683987A patent/JPH02501394A/ja active Pending
  • 1987-10-27 AU AU82338/87A patent/AU8233887A/en not_active Abandoned
  • 1987-11-04 NZ NZ22244887A patent/NZ222448A/xx unknown
• 1989
  • 1989-05-04 FI FI892152A patent/FI892152A/fi not_active IP Right Cessation

Non-Patent Citations (1)

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