IL44729A - Production of an improved lignocellulosic pulp for use in paper industry - Google Patents

Description

The production of ah improved lignocellulosic pulp for use in paper industry VITA MAYER & C. gia F.LLI VITA S.

C/ 42860 It is well known that In order to obtain cheml-mechanlcal pulps It is necessary to treat a llgnocelluloslc material with liquors containing the usual reagents (such as sodium hydroxide, sodium hydroxide plus sodium carbonate, acid sodium sulphite, neutral sodium sulphite, alkalino for sodium oarbonato- oodlum sulphite) in a relatively small amount in order to dissolve the lignin to loosen the bonds between the fibers, without dissolving excessive lignin and carbohydrates.

However, the chemical attack should allow for the subsequent mechanical fiber separation to occur by specific power consumptions of the order of at least one third of tile power normally used for wood pulp production.

It is essential that the power consumption for fiber opening is reduced since, unlike wood pulp, the chemi-mechanical pulps aire of by far higher physical strength.

Generally, this chemical process is accomplished In one step only.

Siis invention relates to a process for producing chemi-mechanlcal pulp by a plurality of chemical and mechanical steps, so as to concurrently provide high yield, brightness and physical strength^.

A process according to the present invention is carried out as follows: Bae wood chips, preferably of a uniform thickness, are steamed to remove entrapped air and to facilitate the next alkaline process step which is carried out to swell the fibers and loosen the bonds thereof. 44729/2 After iber swelling in the alkaline liquor, a coarse defibratlon is carried out, so as to transform the chips into fiber bundles having a diameter of about one millimeter.

However, it is highly desirable not to overdo such an opening or breaking operation, in order not to make the following operations more difficult, if not impossible.

Ihis treatment is followed by hot water washing to reduce the liquor pH and remove most of the materials dissolved in the preceding alkaline treatment.

One material, partially opened and washed, is then processed with an oxidizing solution containing peroxides, and/or persalts, and/or pressurized oxygen, or other oxidising materials· .Che oxidizing operation must be carried out at a suitable pH, ranging from 8 to 11, so that the selected oxidizing agent may be effective at the highest reaction speed possible, but without noticably decomposing the oxidizing agent prior to its reaction with the fibrous material.

!Ehe process temperature (50°-150°C) will depend on the selected oxidizing agent and the oxidizing reaction speed.

Upon completion of the oxidizing process, a solution of sodium bisulphite and sulphite is added to provide a total concentration in SOg in the range of 20-50 g/l and a pH ranging from 4 to 8.

Cooking is then carried out at a ratio of wood to liquid of 1 s 2 and 1 : 6.

The cooking temperature may be 120°-180°C end the cooking time 30 minutes-4 hours.

This treatment serves the purpose of introducing sulfonic groups into the ligno-cellulosic material for improving the mechanical characteristics of the pulp, increasing the bonding capability of the fibers.

Upon completion of cooking, the product is washed, the mechanical defibration is completed and then the pulp is slightly acidified.

She novelty of the present invention resides in the above described sequence.

The step comprising this sequence are all well known per se, but it is just this sequence that enables to provide results never achieved heretofore.

Shis process is particularly useful for providing bright pulps from woods rich in chromophoric substances.

For a better understanding of the inventive process, some not limiting examples will now be given for carrying out the process.

EXAMPLE 1 (Dais example was carried out in accordance with the test Standard CS 665 of the applicant's research section. 100 g poplar chips were steamed for 15 minutes* The chips were then cooled to room temperature with 500 ml liquor containing 15 g/l laOH for 1 hour.

After drying and pressing, the chips were supplied to a disc opener for reducing the fiber bundles to the required, size.

She resulting material was washed with hot water and then mixed with a solution of hydrogen peroxide to add peroxide on dried wood, then adding 3 sodium silicate and 0.05$ MgS04.7H20. me ratio of wood to liquor was 1 : 3· She processing temperature was H0°C for 1 hour. me material was diluted to a wood to liquor ratio of 1 : 5 with a solution of sodium bisulphite and sulphite to pH 6.2, so as to have 13.7$ S02 calculated on the weight of dried wood. me cooking temperature was 130°C for 1 hour. e opening of the fibers was completed and the material washed with a slightly acidified solution to provide a final pH of about 5.

The percentage consumptio of the reactants calculated on the weight of the wood was: HaGH * 18.65$ wt.

H202 « 2.0$ wt.

S02 « 13.75$ wt.

Yield » 87 wt.

Brightness degree « 86.

C.S.F. » 520 Breaking length « 4,900 m. 0 S.E. « 23.7 Burst factor « 2.82 Tear factor « 49 Porosity « 64" EXAMPLE 2 This example was carried out In accordance with the test Standard CS 741 of the applicant's research section. 100 g beech chips were steamed for 15 minutes.

The chips were then processed at room temperature with 500 ml liquor containing 82 g/l HaOH for 1 hour.

Upo complete impregnation, the material was dried and pressed, She chips were then supplied to a disc opener for reducing the size thereof to bundles of a diameter less than 1 mm.

She resulting material was washed with hot wate and then mixed with an amount of hydrogen peroxide to provide 2≠ peroxide on the dried wood, then adding 3% sodium silicate and 0.0 ^ ¾304. H20.

T e ratio of wood to liquor was 1 : 3.

The processing temperature was 20°C for 1 hour and 100°C for the next hour.

The material was diluted to a wood to liquor ratio of 1 : 5 with a solution of sodium bisulphite and sulphite to pH 6.2, so as to have 11.4$ 3Q2 calculated on the weight of dried wood.

Cooking was carried out as follows: Se temperature was raised from 100° to 15O°0 in 110 minutes, and then to the final cooking temperature for 1 hour. The opening of the fibers was completed and the material washed with a slight acidic solution to provide a final pH of about 5.

She percentage consumption of the reactants calculated 44729/2 * Η2°2 β 2?δ S02 11.40 Yield » 81 Brightness degree » 82.7 C.S.F » 305 Breaking length « 4*200 m.

Burst factor « 2.50 Tear factor · 38 Porosity » 78" BXAMKEB 3 Shis example was carried out in accordance with the test Standard OS 708 of the applicant's research section. 100 g maple chips were steamed for 15 minutes.

She chips were then processed at room temperature with 500 ml liquor containing 79.5 gl iJaOH for 1 hour.

Upon complete impregnation, the chips were dried and pressed* and then supplied to a disc opener for reducing the size thereof to bundles of a diameter lees than 1 mm.

She resulting material was washed with hot water and then mixed with a solution of hydrogen peroxide to provide 1.5 peroxide calculated on the weight of dried wood, then adding 3 sodium silicate and 0.05$ Ώιβ ratio of wood to liquor wae 1 : 3.

She processing temperature was 20°C for 1 hour and then 100°C for the next 2 hours.

Finally, the material was reacted with a liquor comprising sodium bisulphite and sulphite to 6.2 pH.

She amount o S02 on the dried wood was 13.8?S.

She ratio of wood to liquor was 1 : 5* Cooking was carried out as follows: Ihe temperature was raised from 100° to 150°C in 2 hours and kept at 150°0 for 2 hours. Ί3αθ opening of the fibers was completed and the material washed with a slight acidic solution to pH 5.

The percentage consumption of the reactante calculated on the weight of the wood was: KaCH a 25.9$ H2°2 s 1·55¾ Yield a 85$ Brightness degree » 81.2

Claims (6)

44729/2 CLAIMS:

1. A process for pulp production at a high, yield, brightness degree and physical strength for use in the paper industry, comprising the following steps: (a) chip steaming for air removal; (b) impregnation of steamed chips with an alkaline solution containing 15-80 g 1 NaOH; (c) stripping of excess alkaline liquor used in step (b); (d) partial opening of the swollen chips to provide fiber bundles of a diameter of about 0.5-4 mm and minimum production of single fibers; (e) washing with water; (f) treating with an oxidizing agent; (g) adding a solution of sodium bisulphite and sulphite at suoh a ratio as to provide a total concentration in !302 being abou 100°-180oC; (h) washing with water; (i) opening completion of the washed material; and (1) acidification.

2. · A process as set forth in Claim 1, wherein the alkaline processing step (b) is carried out at a temperature between room temperature and 100°C.

3. A process as set forth in Claims 1 and 2, wherein the alkaline environment should be at pH higher than 13 and comprises sodium hydroxide and/or sodium hydroxide plus sodium sulphite, and/or sodium hydroxide plus sodium carbonate. 44729/2

4. A process as claimed In Claims 1-3» wherein the partly opened lignooellulosic material is oxidized with a solution of peroxides and/or persalts, and/or gaseous oxygen in the presence of catalysts in alkaline environment, wherei active oxygen is 0.5·3$.

5. A process as set forth in Claim 4» wherein the temperature for the oxidizing step is 50°-150°G.

6. A process as set forth in Claims 4 and 5» wherein the pH of the oxidizing solution varies between 8 and 11. HE:dn