Method for manufacturing papermaking pulp

a technology of papermaking pulp and manufacturing method, which is applied in the field of paper pulp manufacturing process, can solve the problems of pulp whiteness reduction, loss of yield relative to wood, difficulty in bleaching, etc., and achieve the effect of better bleaching

Inactive Publication Date: 2012-05-17
ITT MFG ENTERPRISES LLC +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0048]Specifically, after the ozonation, the acids within the fibers tend to be progressively released. The nature and the duration of the deacidification according to the invention are therefore adapted so as to obtain a stable pH before the bleaching step, thereby making it possible to neutralize all the acid species and obtain better bleaching.

Problems solved by technology

However, the ozone treatment raises particular problems, namely a reduction in the whiteness of the pulp, a subsequent bleaching difficulty, a loss of yield relative to the wood and an increase in the chemical oxygen demand of the bleaching effluents.
None of these approaches is deemed to be satisfactory both as regards the mechanical strength of the pulp, and the optical properties thereof.
That document too does not address the loss of yield observed during bleaching.
However, the methods used in the prior art are not completely satisfactory.

Method used

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  • Method for manufacturing papermaking pulp

Examples

Experimental program
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Effect test

example 1

[0132]A pine pulp was prepared using the TMP process. The pulp underwent an ozone treatment during the refining phase. More precisely, the reject from the primary refiner was treated with 2% ozone, the pH being adjusted by adding 5 kg of caustic soda per tonne of pulp, and then the ozone-treated reject was mixed with the accepted fraction from the secondary refiner. The whiteness of the pulp after the ozone refining / treatment was 47.3%.

[0133]After the ozone refining / treatment, a chelation step was provided, during which the pulp was treated with 4 kg of DTPA per tonne of pulp, with a consistency of 4% and at a temperature of 70° C. and a pH of 6-7 for 1 hour.

[0134]After the chelation step, the pulp underwent a bleaching step, with a consistency of 20%, at a temperature of 70° C. for a time of 2 hours.

[0135]To prepare pulp A (comparative example), the following parameters were also used:[0136]no deacidification step between the ozone refining / treatment and the chelation; and[0137]ble...

example 2

[0156]A pine pulp was prepared using the TMP process. The pulp underwent an ozone treatment during the refining phase. More precisely, the reject from the primary refiner was treated with 2% ozone, the pH not being adjusted, and then the ozone-treated reject was mixed with the accepted fraction from the secondary refiner. The whiteness of the pulp after the ozone refining / treatment was 48.3%.

[0157]After the ozone refining / treatment, a chelation step was provided, during which the pulp was treated with 4 kg of DTPA per tonne of pulp, with a consistency of 2-3% and at a temperature of 70° C. and a pH of 6-7 for 1 hour.

[0158]After the chelation step, the pulp underwent a bleaching step, with a consistency of 20%, at a temperature of 70° C. for a time of 2 hours.

[0159]To prepare pulp E, the following parameters were also used:[0160]a deacidification step lasting 3 hours between the ozone refining / treatment and the chelation, by means of 20 kg of sodium hydroxide per tonne of pulp (7.4 p...

example 3

[0177]A spruce pulp was prepared using the TMP process. The pulp underwent an ozone treatment during the refining phase. More precisely, the reject from the primary refiner was treated with 2% ozone, the pH not being adjusted, and then the ozone-treated reject was mixed with the accepted fraction from the secondary refiner. The whiteness of the pulp after the ozone refining / treatment was 51.2%.

[0178]After the ozone refining / treatment, a chelation step was provided, during which the pulp was treated with 4 kg of DTPA per tonne of pulp, with a consistency of 2-3% and at a temperature of 70° C. and a pH of 6-7 for 1 hour.

[0179]After the chelation step, the pulp underwent a bleaching step, with a consistency of 20%, at a temperature of 70° C. and for a time of 2 hours.

[0180]To prepare pulp I (comparative example) the following parameters were also used:[0181]a deacidification step lasting 5 to 10 minutes between the ozone refining / treatment and the chelation, by means of 10 kg of sodium...

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Abstract

The invention relates to a method for manufacturing papermaking pulp, including: a step of refining wood, including an ozone treatment, so as to obtain a mechanical pulp; a deacidification step including placing the mechanical pulp in contact with a deacidification composition including at least one alkaline agent for more than one hour; and a bleaching step including placing the deacidified pulp in contact with a bleaching composition; wherein the pH varies by less than 0.2 point during the last 30 minutes of the deacidification step, and the pH is 6. to 10 at the end of the deacidification step.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a paper pulp manufacturing process.TECHNICAL BACKGROUND[0002]Paper pulps called “mechanical pulps” or “high-yield pulps” or “wood pulps” are obtained directly from wood by a series of mechanical (defibering and refining) treatments carried out by means of grinders and / or refiners. The pulp may then undergo a bleaching phase in one or more steps.[0003]It is known that an ozone treatment during pulp refining helps to improve the quality of the pulp produced, in particular in terms of physical properties (especially the mechanical strength of the pulp) and to reduce the energy consumption of the process.[0004]However, the ozone treatment raises particular problems, namely a reduction in the whiteness of the pulp, a subsequent bleaching difficulty, a loss of yield relative to the wood and an increase in the chemical oxygen demand of the bleaching effluents.[0005]An ozone treatment as mentioned above is described in document DE...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): D21C1/00
CPCD21B1/16D21C9/153D21C9/147D21C9/10
Inventor CALAIS, CHRISTOPHEHOSTACHY, JEAN-CHRISTOPHE
Owner ITT MFG ENTERPRISES LLC
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