EP1694913A1

EP1694913A1 - Bleached and unbleached fibrous paper pulps and a method for producing the same

Info

Publication number: EP1694913A1
Application number: EP04793748A
Authority: EP
Inventors: Halina Stupinska; Jaroslaw Palenik; Jadwiga Madaj; Slawomir Milczarek
Original assignee: Biotek Sp Z Oo
Current assignee: Biotek Sp Z Oo
Priority date: 2003-10-30
Filing date: 2004-10-27
Publication date: 2006-08-30
Also published as: PL363211A1; WO2005042838A1; WO2005042838B1

Abstract

Highly efficient fibrous paper pulps are produced according to the invention from stems of the plant Sida hermaphrodita Rusby, which is characterised by the absence of resinous substances, lignin contents lower than in the wood, and a high proportion of long phloem fibres. Gaining and preparing a raw material for a technological process is waste-free, low energy-consuming and labour-consuming. Methods for producing pulps according to the invention in a chemothermomechanical process are friendly to the environment, and in particular they are suitable for using in little and mediate enterprises. Products resulting from using the invention have useful properties which are required in manufacturing various types of paper of common usage, are easier processed with papermaking machines than pulps from the wood, because they do not give rise to formation of precipitations of resin acid compounds. Technological waste water can be used to soil fertilization.

Description

Bleached and unbleached fibrous paper pulps and a method for producing the same Technical Field The present invention relates to bleached and unbleached, fibrous paper pulps, and a method for producing unbleached and bleached fibrous paper pulps. Background Unbleached and bleached fibrous paper pulps are produced mainly from softwood and hardwood, as well as from corn straw, fibrous plants, such as hemp, flax, kenaf, sisal, and reed, as well as from bagasse, e.g. waste sugar cane remaining after sugar extraction, from bamboo, sobai grass and esparto. Efforts are made also to process into fibrous paper pulps inter alia elephant's grass, oil plant straw, e.g. rape, toadflax, ricinus, industrial plant straw, e.g. poppy, marsh mallow, white melitot and other plants. The Polish Patent No P348549 discloses also bleached and unbleached cellulose pulps and a process for making the same from a biomass in the form of stems of the perennial plant Sida hermaphrodi ta Rusby. A basic paper raw material, e.g. wood, is one that is very difficult to regenerate (15-30 years), and the most remaining, above-mentioned raw materials are annual plants requiring yearly crops and cultivation. Preparation of wood to the form suitable for producing fibrous paper pulps requires tree cutting, cutting it into logs, barking and, in the case of most known technologicals processes, breaking up into chips. These all processes are energy-consuming and labour- consuming, and they give rise to waste formation. It is only during barking that energy consumption is 3,0-3,6 k h per m³ of wood, water consumption reaches 2 m³ per m³ of wood, and contamination loading in waste water reaches: BZT₃ 0,1-2,6 0₂/m³, ChZT 0,2-6,0 kg 0₂/m³, and the resulting waste in the form of bark requires further disposal. Softwood and hardwood include as its natural components resin substances and fats, which, when not removed in processes for manufacturing highly efficient fibrous pulps, give rise to a plurality of difficulties in a process of manufacturing a paper, in particular precipitation in a paper-making machine. Paper consumption is still increasing in the world, and that's why demand for fibrous paper pulps, in particular highly efficient fibrous pulps to be produced with chemothermomechanical methods which are characterised, approximately at the same productivity from raw materials, by improved useful properties over mechanical pulps, are significantly less expensive than for cellulose and semi-chemical pulps, and in a plurality of applica- tions, as in the most printing papers, blotting papers „tissue", cardboards and in hygiene and sanitary articles, they replace them succesfully. The chemothermomechanical pulps are excelently suitable to be produced in small and mean enterprises, because an economically profitable production volume in such works is several times lesser than that of cellulose and semichemical pulp works. In the process for making highly efficient fibrous paper pulps by the chemothermomechanical method the desintgrated raw material is pre-washed, steamed, and impregnated with the aim to plastify lignin contained therein, in general at a temperature 100-130°C, with chemical agents, such as sodium sulfite, sodium carbonate, sodium hydroxide, as well as hydrogen peroxide. Subsequently, it is mechanically hot disintegrated, and when washed, the resulting pulp is bleached in one or more stages with inter-stage beating and washing, and next sorted, de-watered, and dried. It is an object of the invention to provide unbleached and bleached fibrous paper pulps and a method for producing highly efficient unbleached and bleached fibrous paper pulps from the restorable raw material with a high annual increment of useful mass, wherein technological processes and operations for producing fibrous pulps are simplified, less energy-consuming and labour-consuming, as well as less noxious for the environment against that used actually in the industry, while providing a product, e.g. highly efficient fibrous paper pulps of a quality which is comparable with that of actually produced pulps. Disclosure of the invention The object is achieved through the change of a raw material, as well as the change of a method for producing highly efficient fibrous paper pulps by the chemothermomechanical method. The unbleached and bleached fibrous paper pulps are characterised in that they are produced from stems of the perennial plant Sida hermaphrodi ta Rusby. The inventive process for manufacturing unbleached and bleached fibrous paper pulps from the biomass by using, in an impregnation stage, solutions of sodium sulfate and sodium hydroxide at elevated temperature with mechanically defibering is characterised in that the fibrous pulps are produced from the stems of the perennial plant Sida hermaphrodi ta Rusby. Preferably, a crop of the technologically ripe stems of the plant Sida hermaphrodi ta Rusby is performed with agricultural machines, in particular self-propelled chaff cutters which disintegrate the stems into segments of 10 to 40 mm in length, preferably from 15 to 30 mm. Preferably, it is used directly a part of stems only (or alternatively, a part of stems are directed to the direct processing only) , and the excess of harvested stems in a disintegrated form are stored in the storage yard without preservatives and protective additives against fermentation processes. Preferably, the disintegrated stems are directed to the technological chemothermomechanical process, in which they are impregnated with sodium sulfate and sodium hydroxide solutions at a temperature from 120° to 130°C, in particular at 110°C, for 5-30 minutes, followed by defibering with an inter-stage washing and sorting. Preferably, the disintegrated stems are directed to the technological chemothermomechanical process, in which they are impregnated with hydrogen peroxide and sodium hydroxide solutions at a temperature from 100° to 130°C, in particular at 110°C, for 5-30 minutes, followed by defibering with an inter-stage washing and sorting. Preferably, the resulting pulp from the chemothermomechanical process is bleached with hydrogen peroxide in a basic medium of sodium hydroxide at the concentration 15- 32%, in particular 30%, followed by washing with hot water . Preferably, to wash the unbleached pulp the hot water or effluent from washing the pulp after bleaching is used. Preferably, to wash the bleached pulp the hot water, preferably of a temperature 80°C is used. Preferably, the washed bleached pulp is acidified to pH 3, a then washed with cold water. Preferably, the effluent from washing the pulp after acidification is used to neutralize waste water from washing the pulp before bleaching. Preferably, neutralized process waste water is fed into a waste water treatment plant or used to soil fertilization. The nature of the invention lies in that the highly efficient, ubleached and bleached, fibrous paper pulps are produced from stems of the perennial plant Sida herma- phrodi ta Rusby by a chemothermomechanical method with using, at an impregnation stage, sodium sulfate and sodium hydroxide and hydrogen peroxide at elevated temperature 100-130°C. The crop of technologically ripe stems of this plant is performed using agricultural self-propelled chaff cutters which disintegrate the stems into segments of 10 to 40 mm in length, preferably segments of 15-30 mm in length, which in a such disintegrated form are directed directly to the technological process and washed, steamed, and impregnated with sodium sulfate and sodium hydroxide or sodium hydroxide and hydrogen peroxide to plastify lignin at a temperature 100-130°C, in particular at 110°C, maintaining for 5-30 minutes, ' followed by mechanical action in one or two stages, which gives rise to defibering a swelled raw mateial, or in a reversed order, first defibering, and next maintaining for 30-60 minutes, hot washing, preferably at a temperature 80°C, sorting, and dewatering. An excess of the harvested stem biomass from the plant Sida hermaphrodi ta Rusby is stored in storage yards without preservatives and protectiwe agents against fermentation processes. The unbleached, highly efficient fibrous paper pulps resulting by the inventive method from a raw material in the form of stems of the plant Sida hermaphrodi ta Rusby meet requirements made to an unbleached chemothermo- chemical pulp from wood in a plurality of its applications, and in the case of using sodium hydroxide and hydrogen peroxide at the impregnation stage of the raw material, they can replace for determined papers the bleached chemothermomechanical wood pulps. The resulting fibrous pulp is bleached, preferably at a high concentration 30%, in a single stage or in two stages, with hydrogen peroxide in a basic medium, washed with hot water, preferably of a temperature 80°C, and next defibered or not, depending on an assumed dewatering capacity of the product. Subsequently, it is acidified to pH 3-4 by diluting with cold water with addition of sulfuric acid to the suspension concentration 3-4% for 30 minutes, followed by washing with cold water, dewatering, and drying. The bleached, highly efficient, fibrous paper pulps resulting from a raw material in the form of stems of the plant Sida hermaphrodi ta Rusby by the process of the invention meet requirements made to the bleached chemothermomechanical wood pulp in a plurality of applications. Source of raw materials for producing the fibrous pulps of the invention constitutes is crop plantations of the plant Sida hermaphrodi ta Rusby situated or established near the pulp work. The annual increment of a raw material mass in plantations of this plant is ten times greater than the annual wood increment from the same forest surface, and a crop of raw stems using the self-propelled chaff cutters is simple and not very energy-consuming and labour- consuming. The stems harvested and cut by using self- propelled chaff cutters are directed directly to the technological process or to the storage yard. The raw material does not require barking, and cutting stems into a chaff requires less energy than cutting wood into chips. Energy consumption in producing chemothermomechanical pulp by the process according to the invention, as compared to processing wood raw materials, is lower than about 5 kWh/t of the pulp, and the contamination loading in waste water, as ChZT, is also lower than about 8 kg 0₂/t of the pulp. Morfological structure and chemical composition of stems from the plant Sida hermaphrodi ta Rusby as a raw material are advantageous, a high proportion of phloem fibers is very essential, which is 25-30%, and simultaneously lignin contents is lower than in the wood, e.g. at a level 20%, the cellulose contents being about 41% which is comparable to the amount of cellulose in pine and birch woods, and only traces of fat and resinous contaminations occur.

Description of embodiment examples Example 1 When technologically ripe, the stems of the plant Sida hermaphrodi ta Rusby are cut using a self-propelled field chaff cutter to yield segments of 20-30 mm in length. In such a form the raw material is stored in the storage yard, from where it is transferred in a continuous manner to the first multi-zone, multi-acting extruder with two concurrently rotating screws of Clextral production. In the first zone of the extruder it is brought a hot water, and next, a part of effluent from washing the pulp after bleaching, with the aim to pre-wash the raw material, and in the second zone the consolidation and effluent discharge takes place. The third zone serves to pre-fibering, and in the fourth zone the steam is brought, and sodium hydroxide, hydrogen peroxide, water glass and DTPA (diethylenetriamine pentaacetic acid) are proportioned in amounts 4,0%, 4,5%, 5,0% and 0,3%, respectively, in relation to the raw material, to plastify lignin, which makes it easier to swell fibers and its defibering, as well as pre-bleaching. The temperature in the plasti- fication, zone is about 110°C, and the suspension concentration is about 30%. In the fifth zone defibering the swelled raw material and shortening the phloem fibers take place. In the sixth zone the fibrous pulp is removed from the extruder to a flow retention vat provided with a screw, in which by the end of retention time the flow time is 30 minutes, temperature is 90°C, and the pH value falls from 11 to 8,5. Subsequently, the pulp is fed into the second bi-vis extruder, in the first zone of which it is mixed with waste water from washing the pulp after bleaching, which is a washing liquid. In subsequent three zones, the pulp is washed also with waste water from washing the pulp after bleaching, and in the fifth zone proportioning bleaching agents takes place, e.g. hydrogen peroxide, sodium hydroxide, DTPA (ethylenediamine pentaacetic acid) , water-glass, magnesium sulfate in amounts 3,0%, 2,0%, 0,3%, 3,0%, 0,03%, respectively, in relation to the pulp. In the last two zones subsequent mass defibering takes place, as well as its transferring to the flow retention vat, in which its bleaching is continued at the concentration 30-32%, 90°C, pH from 11 to 9,0 for 60 minutes. From the vat the pulp is fed into the screw press, wherein it is washed with water of temperature 80°C, and next diluted in a pipeline to the concentration 3% with cold water acidified with sulfuric acid to pH 3. When acidified, the pulp is washed in a press with cold water, and an acid waste water from washing the pulp is used to neutralize alkaline waste water from washing the pulp before bleaching. The pulp is purified in hydro- cyclones and directed to dewatering and drying in a dewatering machine. The yield of the bleached pulp from stems of the plant Sida hermaphrodi ta Rusby is 75%, whiteness 85%, and slowness 30°SR.

Example 2 A raw material in the form as in Example 1, is fed into a storage bin, from which it is fed through a washing stand into a steamer, and next to a pressure impregnating machine of Prex type (Pressure Expansion) which is a connection of a screw press and an impregnation tank. To the apparatus, an impregnation solution comprising sodium sulfite and sodium hydroxide, proportioned in amounts of 2,5% and 3,3%, respectively, in relation to a raw material, is proportioned, wherein an impregnation time is 20 minutes. The impregnated raw material is transferred to a heater, in which it is heated at a temperature 110°C for 5 minutes, and next to a pressure mill, in which pre- defibering occurs. Subsequently, the pulp falls through the pressure cyclon to the vat, from where it is pumped to the washing press. The washed pulp is defibered in the second stage mill and sorted, and next dewatered i dried in the dewatering machine. The yield of the unbleached pulp from stems of the plant Sida hermaphrodi ta Rusby is 85%.

Claims

1. Unbleached and bleached fibrous paper pulps, characterised in that they are produced from stems of the perennial plant Sida hermaphrodi ta Rusby.

2. A method for producing unbleached and bleached fibrous paper pulps from a biomass by using, at an impregnation stage, sodium sulfate and sodium hydroxide solutions or hydrogen peroxide and sodium hydroxide solutions at elevated temperature with mechanically defibering, characterised in that the fibrous pulps are produced from stems of the perennial plant Sida herma phrodita Rusby.

3. The method as claimed in claim 2, characterised in that the crop of technologically ripe stems of the plant Sida hermaphrodi ta Rusby is performed with agricultural machines, preferably self-propelled chaff cutters which disintegrate stems into segments of 10 to 40 mm, in particular 15-30 mm in length.

4. The method as claimed in one of claims 2 or 3, characterised in that it is used directly a part of stems only (or alternatively a part of stems only is directed to directly processing) , and an excess of the harvested stems in the disintegrated form are stored in the storage yards without preservatives and protective additives against fermentation processes.

5. The method as claimed in one of claims 2 or 3, charcterised in that the disintegrated stems are directed to the chemothermomechanical process, in which they are impregnated with a sodium sulfite solution at a temperature from 100° to 130°C, preferably at a temperature 110°C, for 5-30 minutes, followed by defibering with inter-stage washing, and sorting.

6. The method as claimed in claim 4, characterised in that, the disintegrated stems are directed to the chemothermomechanical process, in which they are impregnated with a sodium sulfite and sodium hydroxide solution at a temperature from 100° to 130°C, preferably at a temperature 110°C, for 5-30 minutes, followed by defibering with an inter-stage washing, and sorting.

7. The method as claimed in one of claims 2 or 3, characterised in that the disintegrated stems are directed to the technological chemothermomechanical process, in which they are impregnated with a solution of hydrogen peroxide and sodium hydroxide at a temperature from 100° to 130°C, preferably at a temperature 110°C, for 5-30 minutes, followed by defibering with an inter-stage washing, and sorting.

8. The method as claimed in claim 4, characterised in that the disintegrated stems are directed to the technological chemothermomechanical process, in which they are impregnated with a solution of hydrogen peroxide and sodium hydroxide at a temperature from 100° to 130°C, preferably at a temperature 110°C, for 5-30 minutes, followed by defibering with an inter-stage washing, and sorting.

9. The method as claimed in claim 5, characterised in that the pulp resulting from the chemothermomechanical process is bleached with hydrogen peroxide in a basic medium of sodium hydroxide at a concentration 15-32%, preferably at a concentration 30%, followed by washing with hot water.

10. The method as claimed in one of claims 6 or 8, characterised in that the pulp resulting from the chemothermomechanical process is bleached with hydrogen peroxide in a basic medium of sodium hydroxide at a concentration 15-32%, preferably at a concentration 30%, followed by washing with hot water.

11. The method as claimed in claim 7, characterised in that the pulp resulting from the chemothermomechanical process is bleached with hydrogen peroxide in a basic medium of sodium hydroxide at a concentration 15-32%, preferably at a concentration 30%, followed by washing with hot water.

12. The method as claimed in claim 5, characterised in that it is used for washing the unbleached pulp the hot water or effluent from washing the pulp after bleaching.

13. The method as claimed in one of claims 6 or 8, characterised in that it is used for washing the unbleached pulp the hot water or effluent from washing the pulp after bleaching.

14. The method as claimed in claim 7, characterised in that it is used for washing the unbleached pulp the hot water or effluent from washing the pulp after bleaching.

15. The method as claimed in one of claims 9 or 11, characterised in that it is used for washing the bleached pulp the hot water, preferably of a temperature 80°C, .

16. The method as claimed in claim 10, characterised in that it is used for washing the bleached pulp the hot water, preferably of a temperature 80°C, .

17. The method as claimed in claim 15, characterised in that the washed bleached pulp is acidified to pH 3, followed by washing with cold water.

18. The method as claimed in claim 16, characterised in that the washed bleached pulp is acidified to pH 3, followed by washing with cold water.