GB1564084A - Method of manufacturing mechanical pulp for paper making from waste sisal fibre - Google Patents

Description

(54) A METHOD OF MANUFACTURING MECHANICAL PULP FOR PAPER MAKING FROM WASTE SISAL FIBRE (71) We, DAISHOWA ENGINEERING CO. LTD., a Company organised and existing under the laws of Japan, of 798 Hina, Fuji-city, SHIZUOKA Pref., 417 Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a method of manufacturing mechanical pulp for paper making from waste sisal fibre which gets in the process of decorticating sisal leaves.

Sisal is a tropical perennial plant having nomen "agave sisalana perrine" and is planted widely in tropical countries, e.g., Tanzania, Kenya, Brazil and Mexico. Young plants are raised in nursery about twelve months and are transplanted. After about eighteen months green leaves can be harvested. A sisal plant produces about 3 to 4 leaves monthly or 36 to 48 eaves annually. The green leaves of sisal are harvested every 6 to 9 months for each plant.

The weight of one leaf differs widely according to planting conditions and plant breedings and is around 700 gramms. Each green leaf contains about 5% by weight of fibrous material. The other materials are water and non fibrous material. About 90% by weight of the fibrous material which is derived on the process of decortication of sisal leaves is utilized as material of sisal rope. The other 10% of the fibrous material is mixture of short fibers and fleshy matters and is called as waste sisal fibre. A portion of the waste sisal fibre is utilized as cushion material in chairs and beds, and as bags. However, large portions of the waste fibre are discarded.

The plantation area of the sisal in the world is about one million hectares and production of sisal fibre is about 650,000 tons annually. Thus, the waste sisal fibre is discarded about 70,000 tons annually and can be used as raw material in industrial production. Further, main production region of sisal in Africa lacks sufficient forest to produce wood pulp so that papers must be imported. Consequently, if the waste sisal fibre can be utilized as raw material of pulp, profit of sisal plantation is improved and sum of paper import is reduced.

Accordingly, it is a primary object of the present invention to provide a new method of manufacturing high quality pulp and paper from waste sisal fibre.

It is an object of the present invention to effectively utilize waste sisal fibre as raw material of pulp in economically comparable cost with wood pulp.

It is another object of the present invention to raise pulp and paper manufacturing factories utilizing waste sisal fibre as a new industry in sisal production countries.

To attain above mentioned objects, a method of manufacturing pulp and paper, according to the present invention includes following steps of: starting from waste sisal fibre produced while sisal fibre producing process from sisal leaves, cutting the waste sisal fibre below 100 millimeter (mm.) in statistical mean length, pre-refining the cut sisal fibre at a consistency below 10% in a pre-refiner, thickening the low consistency slurry obtained from the pre-refiner, and refining the thickened slurry in one or more refiners successively to obtain pulp.

By pre-refining cut sisal fibre in a pre-refiner at low consistency, the slurry obtained from the pre-refiner can be refined easily by refiners which are used in wood pulp manufacturing equipment. The pre-refiner itself may be one of known disk type refiner. By the above mentioned process, pulp manufacturing plant from the waste sisal fibre can be designed easily.

Further, as described later, lignin content in the sisal fibre is far less than that of woods, so that effluent treatment is also easy.

According to a feature of the present invention, heat is applied while said pre-refining proceeds.

According to another feature of the present invention, low concentration of chemicals of alkali agent and alkaline reducing agent is added while said pre-refining proceeds.

The features and advantages of the present invention will become apparent to those skilled in the art upon reviewing the following detailed description and drawings, by way of example, in which: Figure 1 is an illustration of sisal and a diagrammatic flow sheet of a manufacturing process from waste sisal fibre to pulp; Figure 2 shows one sisal leaf and an enlarged sectional view along A-A of the leaf; and Figure 3 shows a sectional view of a sisal fibre.

As described before, in sisal fibre production plant, green leaves L are cut from sisal plant S and are conveyed through a conveyor 1 to a decorticator 2 to produce good sisal fibre Ha which is utilized to produce sisal ropes. Among fibrous material contained in the sisal leaves, 90% is used as raw material of the sisal ropes and 10% is discarded as waste sisal fibre Hb which is formed by shorter and non-uniform fibre.

The analysis of the waste sisal fibre Hb is shown in TABLE I and shows that the fibre is superior raw material for pulp physically and chemically.

Table I Conife- Broad Manila rous leaf Sisal hemp wood wood Element fibres length mm. 1.5-4 3-12 3 1 width 11 20-30 16-32 30-55 13-25 Chemical composition of material % Cellulose 75.8 65.9 49-58 51-58 Lignin 6.5 11.6 26-31 18-24 Pentosan 21.7 20.4 10-12 21-26 Resins 1.1 2.7 1.9-3.9 0.6-3.8 Ash 1.0 0.6 0.1-0.4 0.2-1.0 As shown in the Table, the element fibre F' of the sisal fibre F has intermediate values in length and width compared with coniferous and broad leaf woods. The chemical composition of the sisal fibre shows that cellulose content is much more and lignin is much less compared with the woods. Thus, the waste sisal fibre is more preferable as raw material of pulp than coniferous and broad leaf woods.

Ordinary raw material of wood pulp is called chips which are small blocks of wood.

However, the waste sisal fibre Hb is formed as bulky entwined block of fibre, so that ordinary refining equipments for wood pulp cannot be utilized for sisal pulp. According to the present invention treatment processes from the waste sisal fibre to refiner of pulp mill are disclosed.

The waste sisal fibre Hb from the decorticator 2 is dried in the sun and is cut by a cutter 3 less than 100 mm., preferably between 2 - 100 mm. The cut fibre is fed to pre-refiner 4 through a belt conveyor 5 and a feeder 6. When mean value of the cut length is below 2 mm., produced pulp fibres will be too short, and when the cut length is more than 100 mm., plugging of the feeder 6 may be the result. The length of the cut fibre expresses statistical mean length, e.g., 100 mm. expresses mean value of the cut fibre is 100 mm. and includes about 68% of the fibre within 80 mm. - 120 mm. length.

The refining treatment in the pre-refiner 4 is performed to remove latency of the sisal fibre F. The consistency of the fibre is below 10%, i.e., 10 weight portions of the fibre and 90 weight portion of solution of water or water added by chemicals, and preferably between 2 - 6%. By the pre-refining, fiberizing and hydration of the fibre are promoted, length of the fiberized fibre is uniform, following primary and secondary refining processes are easily performed, too fine fibre is not produced, and fibrillation of produced element fibres is promoted.

While the pre-refining proceeds, heat treatment by hot water or steam may preferably be performed, and the temperature range may be 300C - 80"C, preferably 60"C. Also, low concentration chemicals of alkali agent and alkaline reducing agent, e.g., 1 - 5 weight % to sisal cut fibre, are also preferably added. The chemicals may be caustic soda and/or sodium sulfite. By the heat and chemicals treatment, latency of the fibre is removed, shives are reduced, and flexibility of fibers is promoted. The refiner 4 may be disk type refiner rather than cone type refiner.

The waste sisal fibre Hb includes about 10% of impurities, e.g., epidermis, metal and sand, which must be removed before or while pulping process. In the illustrated process, the impurities are removed before the pre-refining process. The cut fibre He is supplied by the conveyor to the feeder 6, in which the impurities are separated from the cut fibre He which is fed to the pre-refiner 4. To the feeder 6, the above mentioned heat treatment steam 7, the chemicals 8 and the water 9 are added. A metered quantity of mixture of the cut fibre Hc and the solution is fed to the pre-refiner 4.

As described, by low consistency treatment of the cut fibre in the pre-refiner 4, length of fibre is uniform, fiberizing and hydration of fibre are promoted, primary and secondary refining processes are easily performed and latency of the cut fibre is removed.

The cut sisal fibre Hc is wetted in the feeder 6 and is metered and supplied continuously to the pre-refiner 4. Slurry from the pre-refiner 4 is fed through a chest 10 to a thickner 11 where the slurry is washed and thickened. The slurry which is now predetermined high consistency is fed through a primary refiner 12 and a chest 13 to a secondary refiner 14.

After the primary refiner 12, process and equipment may be applied as well known process from wood chips to manufacture pulp.

Table II shows examples of slurrys after the pre-refiner 4 when length of the cut sisal fibre Hc and consistency of pre-refining are varied.

Table II (I) (11) (III) (IV) (V) Mean length of cut fibre 5 50 50 50 100 mm.

Consistency % 2.5 3.9 6.1 4.7 3.6 Freeness ml. 690 740 735 790 720 Fibre classification 24 mesh on % 65.5 63.6 64.1 60.1 65.8 42 mesh on % 11.3 17.4 12.3 14.0 12.1 80 mesh on % 10.9 11.4 9.4 12.2 14.1 150 mesh on % 7.8 6.3 6.4 8.0 9.4 In the table, e.g., example (I), the mean length of cut fibre is 5 mm. and consistency of treated fibre in the pre-refiner is 2.5%. The freeness is measured from slurry according to TAPPI Standard method.

the fibre classification is measured by a series of stepped tanks which are separated by a filter respectively having a mesh of above mentioned order. A predetermined quantity of slurry from the pre-refiner is supplied to uppermost tank which is separated by 24 mesh filter with next stage tank. The slurry flows down sequentially to lower tank and filtrate passed through coarse filter is filtered by fine filter. The percentage in the table shows rate of quantity of filter cake in each filter to quantity of solid fibre supplied to the upper-most tanB.

The Table II shows that slurry passed through the pre-refiner 4 is suitable as raw material of pulp and is easily handled by ordinary primary refiner to manufacture wood pulp.

The slurry from the pre-refiner 4 is thickened to consistency about 20-30% which is higher than consistency of fibre fed to the pre-refiner, and is fed to the primary refiner 12.

The slurry passed the secondary refiner 14 is named as sisal pulp and can be readily used to manufacture paper.

Table III shows examples of freeness of the sisal pulp and physical properties of paper made by the sisal pulp.

Table III (I) (Il) (III) Chemicals - - NaOH Freeness of slurry ml. 450 210 170 Paper density g/cm3 0.42 0.48 0.49 burst factor 18 27 33 breaking length m. 3460 4500 5610 tear factor 92 95 120 brightness % 52 53 49 The data are measured according to TAPPI Standard.

As shown in Table III, excellent paper is manufactured by waste sisal fibre. The Table III shows that, when the pulp is treated by NaOH solution, brightness is reduced a little. Also, the Table III shows that strength is increased as freeness of sisal pulp is decreased.

It will be appreciated that the present invention discloses that the waste sisal fibre can be utilized efficiently and economically as raw material of pulp, by passing the cut fibre through the pre-refining process at low consistency according to the present invention.

Thus, discarded waste sisal fibre can be transformed into paper industrially.

WHAT WE CLAIM IS: 1. A method of manufacturing pulp for paper making from a waste sisal fibre produced as a by-product from sisal leaves in a sisal fibre producing process which comprises cutting the waste sisal fibre to a statistical mean length below 100 mm., pre-refining the cut sisal fibre at a consistency below 10% in a pre-refiner, thickening the low consistency slurry obtained from the pre-refiner, and refining the thickened slurry in one or more refiners successively to obtain a sisal pulp.

2. A method as claimed in Claim 1, in which heat is applied during pre-refining.

3. A method as claimed in Claim 1 or 2, in which an alkaline agent or alkaline reducing agent is added during pre-refining.

4. A method as claimed in Claim 3, wherein from 1 to 5% by weight, based on cut sisal fibre of the alkaline agent or alkaline reducing agent is added.

5. A method as claimed in any of the preceding claims, wherein the cut sisal fibre is pre-refined to a consistency of 2 to 6%.

6. A method as claimed in Claim 1, and substantially as hereinbefore described with reference to the accompanying drawing.

7. Paper produced from pulp manufactured by a method as claimed in any of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. Table III (I) (Il) (III) Chemicals - - NaOH Freeness of slurry ml. 450 210 170 Paper density g/cm3 0.42 0.48 0.49 burst factor 18 27 33 breaking length m. 3460 4500 5610 tear factor 92 95 120 brightness % 52 53 49 The data are measured according to TAPPI Standard. As shown in Table III, excellent paper is manufactured by waste sisal fibre. The Table III shows that, when the pulp is treated by NaOH solution, brightness is reduced a little. Also, the Table III shows that strength is increased as freeness of sisal pulp is decreased. It will be appreciated that the present invention discloses that the waste sisal fibre can be utilized efficiently and economically as raw material of pulp, by passing the cut fibre through the pre-refining process at low consistency according to the present invention. Thus, discarded waste sisal fibre can be transformed into paper industrially. WHAT WE CLAIM IS:

1. A method of manufacturing pulp for paper making from a waste sisal fibre produced as a by-product from sisal leaves in a sisal fibre producing process which comprises cutting the waste sisal fibre to a statistical mean length below 100 mm., pre-refining the cut sisal fibre at a consistency below 10% in a pre-refiner, thickening the low consistency slurry obtained from the pre-refiner, and refining the thickened slurry in one or more refiners successively to obtain a sisal pulp.

2. A method as claimed in Claim 1, in which heat is applied during pre-refining.

3. A method as claimed in Claim 1 or 2, in which an alkaline agent or alkaline reducing agent is added during pre-refining.

4. A method as claimed in Claim 3, wherein from 1 to 5% by weight, based on cut sisal fibre of the alkaline agent or alkaline reducing agent is added.

5. A method as claimed in any of the preceding claims, wherein the cut sisal fibre is pre-refined to a consistency of 2 to 6%.

6. A method as claimed in Claim 1, and substantially as hereinbefore described with reference to the accompanying drawing.

7. Paper produced from pulp manufactured by a method as claimed in any of the preceding claims.