US3711366A

US3711366A - Digesting lignocellulosic material with sodium hydroxymethylsulfonate

Info

Publication number: US3711366A
Application number: US00074469A
Authority: US
Inventors: J Nakano; Y Sumi; M Nagata
Original assignee: Kokusaku Pulp Ind Co Ltd
Current assignee: Kokusaku Pulp Ind Co Ltd
Priority date: 1966-08-03
Filing date: 1970-09-22
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16

Abstract

IMPROVEMENT IN A PROCESS FOR MANUFACTURING HIGH YEILD PULP IN WHICH COOKING TREATMENT AND MECHANICAL DEFIBRATION FOR LINOCELLULOSIC MATERIAL ARE COMBINED, SAID COOKING TREATMENT BEING CARRIED OUT IN ALKALINE CONDITION EMPLOYING A SULFOMETHYLATION AGENT WHICH IS PRODUCED FROM ADMIXING SODIUM SULFITE AND/OR SODIUM BISULFITE, FORMALDEHYDE AND WATER, SAID MECHANICAL DEFIBRATION BEING CARRIED OUT EITHER BEFORE OR AFTER THE COOKING.

Description

United States Patent 3,711,366 DIGESTING LIGNOCELLULOSIC MATERIAL WITH SODIUM HYDROXYMETIIYLSULFONATE Junzo Nakano, Yuichiro Sumi, and Makoto Nagata, Tokyo, Japan, assignors to The Kokusaku Pulp Industry Co., Ltd., Tokyo, Japan No Drawing. Continuation-impart of application Ser. No. 657,526, Aug. 1, 1967. This application Sept. 22, 1970, Scr. No. 74,469

Claims priority, application Japan, Aug. 3, 1966, 41/50,503

Int. Cl. D21b 1/16 US. Cl. 162-24 5 Claims ABSTRACT OF THE DISCLOSURE Improvement in a process for manufacturing high yield pulp in which cooking treatment and mechanical defibration for lignocellulosic material are combined, said cooking treatment being carried out in alkaline condition employing a sulfomethylation agent which is produced from admixing sodium sulfite and/or sodium bisulfite, formaldehyde and water, said mechanical defibration being carried out either before or after the cooking.

This application is a continuation-in-part of the copending Ser. No. 657,526, filed on Aug. 1, 1967, now abandoned.

Various processes for producing high yield pulp have been suggested. High yield pulp has already been obtained by groundwood, chemigroundwood and semichemical pulping processes but the high yield pulp so produced contains more lignin than the conventional chemical pulp and, therefore, beating and refining have little effect, no or less fibrillation results, and the strength of the paper produced therefrom is relatively low. Thus, a process for making high yield pulp which is easily beaten and refined to produce a high strength paper is desired.

A sulfite process for red pine native to Japan employing formaldehyde as additive was disclosed in the Journal of the Chemical Society of Japan, Industrial Chemistry Section 54, 195 and 397, 151 and 56, 277. Phenolic compounds in the raw material reacted with the formaldehyde in the sulfite cooking liquor and condensation reaction, which was considered to cause burnt cook, between. the phenolic compounds and lignin was avoided. This process was useful for cooking red pine chips containing heart wood. E. Adler and L. Stockman disclosed in the Svensk Papperstidning 54, 477 that wood was subjected to chemical pulping process using sulfite cooking liquor containing formaldehyde where burnt cook was observed and it was considered that pulping is impossible.

Sodium sulfite or sodium bisulfite, formaldehyde and water are reacted to obtain sodium hydroxymethylsulfonate by the following reactions:

In the case of Reaction 1, it is recognized that about by weight of the original sodium sulfite is converted into sodium hydroxymethylsulfonate under the conditions described hereinafter in the examples; the resulting aqueous solution has a pH range of about 12.4 and 12.7. The aqueous solution contains sodium sulfite, formaldehyde, sodium hydroxymethylsulfonate and sodium hydroxide.

In Reaction 2, the sodium bisulfite is quantitatively converted into sodium hydroxymethylsulfonate and the resulting solution shows a pH of about 4.5. An alkali should be added to maintain the pH value in near neutral to alkaline condition, i.e. at a pH from 5.7 to 13.7.

"ice

In the case of Reactionl, some of the Na SO added is converted into HOCH SO Na and the remaining is maintained in its original state, and, in the case of Reaction 2, all of the Nal-ISO added isconverted into HOCH SO Na if Na SO NaHSO HCI-IO are employed, the following reaction would occur:

Thus, the composition of the liquid formed is complicated and it is difiicult to analyze the composition by a conventional method. It is, however, possible to measure the pH value from which the amount of NaOzl-I may be interpreted. Thus, the equilibrium values of the constituents can be estimated from the degree of formation of NaOH. It is necessary to adjust the pH value of the liquid to the range abovementioned.

The sulfomethylation agent produced as above reacts with lignin. Details of the reaction have not been confirmed, but it seems that:

(1) addition reaction of formaldehyde and the aromatic ring in lignin occurs to form an alcoholic hydroxy group; subsequently the hydroxy group is sulfonated with sodium sulfite or bisulfite to form sulfomethylated lignin;

(2) ortho position to phenolic hydroxy group in lignin is directly sulfomethylated with sodium hydroxymethylsulfonate; and

(3) in addition to the above, the side chain portion in lignin may also be sulfomethylated.

Lignocellulosic materials including soft and hard wood, straw, bamboo, grass and like are cooked by the aqueous solution when the lignin is sulfomethylated according to the above reactions. Of course, side-reactions occur, for example, between other chemicals such as sodium sulfite, sodium bisulfite and sodium hydroxide and non-cellulosic materials such as lignin, hemicellulose and others.

In cooking, that part of the lignin which does not com,- bine with carbohydrates is dissolved in the cooking liquor, While the lignin that combines with the carbohydrates is not dissolved but is converted into a hydrophilic and soft state by sulfomethylation. The resulting cooked material is easily defibrated mechanically without fiber shortening and specific fiber damage. 7

Pulp so treated contains a larger amount'of lignin than the conventional chemical pulps, so the yield of pulp according tothis invention is high. Furthermore, since the lignin is in a hydrophilic and soft state, fiber containing such lignin is easily fibrillated by beating and refining.

Alternatively, lignocellulosic material predefibrated by, for example, grinder and refiner can then be cooked with the aqueous sulfomethylation agent solution.

Oneway of carrying out the present invention is to carry out the cooking under elevated pressure and temperature employing a large amount of the aqueous sulfomethylation agent solution; this is similar to liquid phase cooking process. Another way is to immerse the lignocellulosic material in the cooking liquor, then remove excess liquor, and subsequently, heat the lignocellulosic material by steam as in the conventional vapor phase cooking process. In this case, the cooking time and liquid ratio would be decreased.

The cooking conditions employed in this invention are a temperature of about C. to C., a pressure of about 0.5 kg./cm. gauge to 16 kg./cm. gauge, and the molar ratio of formaldehyde to sulfite and/or bisulfite of 0.8 to 1.2, and, in the liquid phase cooking, a time of 20 minutes to 5 hours, a liquid ratio of 2 to 20, preferably 3.5 to 8 and a concentration of cooking liquor of about 5.to 30% by weight calculated as S0 for lignocellulosic Liquid ratio the volume of the liquor added +Water in the wood chip (1.) the oven-dried weight of wood chip (kg) When lignocellulosic material is processed according to this invention thepH value of the cooking liquor decreases as the reaction-proceeds, because an acid is produced from the lignocellulosic material and sodium hydroxide is consurned by thereaction. However, it is desirable to bring the pH value of the cooking liquor to a pH of-10.9 to l3.7, more suitably 1'1. 9 to 12.7 when cooking treatment is started, and the end pointwill befrom 10.6 to 5.7, more suitably 9.6 to 6.7. Therefore, an alkali should be added to the cooking liquor produced from sodium bisulfite and formaldehyde to bring the pH within the range mentioned above. In any case, care should be taken throughout the cooking treatment to avoid an extremely acid condition.

The pulp produced in accordance with this invention has a brightness of 47% to 53% and a light yellow colour. It is useful as unbleached pulp, but, if desired, it can be bleached 'with hydrogen peroxide to increase brightness to about 70% Preferred embodiments of the present invention will be given by way of examples 'in which the novel process is successfullycarried out.

EXAMPLE 1 material was immersed in the solution and the excess solutionwas removed at which'the pH value of the solution was 8.1". The immersed material was vapor phase cooked at a temperature of 148 C. under a pressure of 4.5 'kg./ cm. gauge for 8 minutes under the conditions of a liquid ratio of 1.6 anda S0 concentration of 4.1%, and then defibratedfor 2 minutes at the sametemperature. The pH value of th'e' cooking solution after defibration was 3.5. The yield-of pulp after defibration was 89.8%. The pulp so obtained had a freeness of 780 cc. (CSE) and'even after treatment with a La'mpenmill for 5 hours the freeness was 770cc. '(CSF); The' decrease in freeness was extremely small. This was similar .to pulp produced by the Asplund'process in which lignocellulosic material was immersed in cooking liquor containing 51.5 g. of sodium sulfite per liter, after removing the excess liquor heated at temperature of 148C. for one hour by steam and defibrated at that temperature. Both pulps were unsatisfactory for use of paper. Furthermore, wood chips were processed with a similar aqueous sulfomethylation agent solution having pHvalue of 5.0; the pH value after the cooking reached 2.2. The resulting pulp had a dark brown colour, so that it could not be employed for paper industry. These phenomena support the idea that an extreme acid condition throughout cooking treatment should be avoided.

' EXAMPLE 2 Mixed chips of six kinds of hard wood native. to Hokkaido, Japan, weighing 375 g. (oven dried weight was 300 g.) were evacuated. 2325 ml. of cooking liquor containing 51.6 g. of SQdiurn sulfite and 11.3 got formaldehyde 4 per liter (the molar ratio of formaldehyde to sulfite being 0.9, a liquidratio being 8.0 and a S0 concentration being 20.3%) and having a pH of 12.7 was added to the chips. Cooking treatment was carried out at a temperature of 150 C. under a pressure of 5 kg./cm. gauge for 30 minutes. The pH value at end of the cooking was 7.9. The cooked chips were separated from the cooking liquor and defibrated in a Bauer laboratory disk refiner and the'knots were removed therefrom. The pulp so obtained was treated by a Lampen mill and thenprepared into handsheets having basis weight of 63 g./m. by TAPPI standard.

For comparative purposes the same procedure as above was carried out,.except that the cooking liquor contained onlysodium sulfite. Characteristics of the pulps and strength of the handsheets are given in Table 1.

TABLE 1 Present invention Control Yield of pulp after defibration, percent 84. 7 85.3 Beating time (hours and minutes) 1. 05 1.05 Freeness (OSF cc.) 2-05 1105 Brightness, percent 44. 2 43. 2 Breaking length (k 6. 1 4. 5 Burst factor 3. 5 2. 3 Tear factor 55 49- MIT folding endurance 35 8 EXAMPLE 3 375 g. of chips and cooking liquor (the molar ratio of formaldehyde to sulfite being 0.9), the same .as in Example 2, were employed. The evacuated chips were immersed in the cooking liquor until they had absorbed 480 to 500 ml. of the cooking liquor. The chips so treated were charged into a laboratory defibrator and vapor phase cooked at 148 C. under a pressure of 4.5 kg./cm. gauge for 4 minutes under the conditions of a liquid ratio of 1.6 and a S0 concentration of 4.1%, and subsequently'defibrated at the same temperature for 2 minutes. The pH value of the cooking liquor aftertdefibration was 9.6. Y

The same kind of chips werevapor phase cooked and defibrated under the same conditions as in the above procedure except that the aqueous solution contained 171 g./l. of sodium sulfite and the cooking time was 60 minutes. 1

Handsheets were prepared as described in Example 2 from both pulps.

Thecharacteristics of the pulps and handsh'eets are EXAMPLE 4 Spruce chips were defibrated by disc refiner and the fine portion was removed, g. of resulting fibers (oven dried weight being 88.7,. g.) was added to 1000 ml. of aqueous solution containing 50 g. of sodium sulfite and 11 g. of formaldehyde (the molar ratio of formaldehyde to sulfite being 0.9, a liquid ratio being 11.4 and a S0 concentration being 27.7%). Cooking was carried'out' at a temperature of 150 C. under a pressure of 5 log/cm. gauge for 2 hours. The pulp thus obtained was beaten in Lampen mill and prepared into haudsheets. The results are shown in Table 3.

EXAMPLE 5 The procedures described in Example 4 were followed but the cooking temperature and pressure were changed to 110 C. and 1 kg./cm. gauge. The results are shown in Table 4.

TABLE 4 Pulp yield, percent 95. 9 95. 9 Beating time (hours and minutes) 1. 2.00 Freeness (CSF cc.) E50 220 Breaking length (km.).. 3. 9 4. 6 Burst factor 1. 5 2. 2 Tear factor 36 2.9 MIT folding enduran 4 9 EXAMPLE 6 375 g. of the same chips as in Example 2 were added to 2325 ml. of cooking liquors, one of which contained 21.3 g. of sodium bisulfite, 25.8 g. of sodium sulfite and 11.3 g. of formaldehyde per liter and had a pH value of 11.9 (Batch I) and another of which contained 51.6 g. of sodium sulfite and 11.3 g. of formaldehyde and had a pH value of 12.7 (Batch II). The molar ratio of formaldehyde to bisulfite and sulfite (Batch I) or sulfite (Batch II) was 0.9.

The pH values of the liquors after immersing of the chips were 11.1 (Batch I) and 12.0 (Batch II).

The cooking treatment conditions were the same for Batches I and II- a temperature of 150 C. under a pressure of 5 kg./cm. gauge for two hours under the conditions of a liquid ratio of 8.0 and a S0 concentration of 20.3%. The pH values at the end of the cooking were 6.7 (Batch I) and 7.7 (Batch II).

On the other hand, for the purpose of comparison, the procedures described above were followed but the cooking liquor contained 42.6 g. of sodium bisulfite and 11.3 g. of formaldehyde and had a pH value of 4.6 (Batch III). The pH value of the liquor after immersing of the chips was 4.6. The pH value at the end of the cooking was 3.5.

The chips separated from the cooking liquor were defibrated in a Bauer laboratory disk refiner and knots were removed therefrom. The pulps so obtained from Batches I, II and III were treated by a Lampen mill and then prepared into handsheets having a basis weight of 63 g./m. by TAPPI standard.

The characteristic of pulps and the strength of handsheets are given in Table 5.

TABLE 5 Batch I II III pH of cooking liquor 11. 9 12. 7 4. 6 Yield of pulp after defibration, percent 80. 8 79. 8 79. 5 Beating time (min) by Lampen 111111.. 45 36 P5 Freeness (C SF cc.) 315 310 325 Brightness, percent 47. 3 48. 5 31. 0 Breaking length (km. 5. 6 5. 9 2. 8 Burst factor 3. 3 3. 9 1. 2 Tear factor 58 66 52 MIT folding endurance 33 52 2 These results show that it is desirable to maintain the pH value of cooking liquor in near neutral to alkaline condition during cooking.

EXAMPLE 7 Spruce chips weighing 375 g. (oven dried weight being 300 g.) were evacuated. 1725 ml. of cooking liquor containing 50 g. of sodium sulfite and 11.9 g. of formaldehyde per liter (the molar ratio of formaldehyde to sulfite being 1.0) and having a pH of 12.7 was added to the chips. Cooking treatment was carried out at a temperature of C. under a pressure of 5.7 kg./cm. gauge for 40 minutes under the conditions of a liquid ratio of 6.0 and a S0 concentration of 14.9%. The pH value at end of the cooking was 7.7. The cooked chips were separated from the cooking liquor and defibrated in a Bauer laboratory disk refiner. The resulting pulp was beaten and prepared into handsheet as described in Example 2.

The results are given in Table 6.

EXAMPLE 8 Spruce chips weighing 375 g. (oven dried weight being 300 g.) were evacuated. 1725 ml. of cooking liquor containing 30 g. of sodiumsulfite and 5.7 g. of formaldehyde per liter (the molar ratio of formaldehyde to sulfite being 0.8) and having a pH of 12.5 was added to the chips (Batch IV). Cooking treatment was carried out at a temperature of C. under a pressure of 7.5 kg./cm. gauge for 80 minutes under the conditions of a liquid ratio of 6.0 and a S0 concentration of 9.0%. The pH value at end of the cooking was 7.1.

The procedures described above were followed but the cooking liquors contained 30 g. of sodium sulfite and 7.2 g. of formaldehyde (the molar ratio of formaldehyde to sulfite being 1.0) (Batch V), and 30 g. of sodium sulfite and 8.6 g. of formaldehyde (the molar ratio of formaldehyde to sulfite being 1.2) (Batch VI). In Batches V and VI, the pH values of the liquor before immersing of the chips and at the end of the cooking were 12.6 and 7.2, respectively.

The cooked chips were separated from the cooking liquor and defibrated in a Bauer laboratory disk refiner. The resulting pulps were beaten and prepared into handsheets as described in Example 2.

The results are given in Table 7.

What is claimed is: 1. A process of making high yield pulp, said process comprising in combination:

(A) cooking treatment of lignocellulosic material, and (B) mechanically defibrating lignocellullosic material, (1) said cooking treatment being carried out in an aqueous cooking liquor by means of sodium hydroxymethylsulfonate at a temperature of 100 C. to C. for a period of time from a few minutes to 5 hours, at a liquid ratio of 1.0 to 20;

(i) said cooking liquor containing active pulping chemicals consisting essentially of an admixture selected from the group consisting of:

(a) sodium sulfite and formaldehyde;

(b) sodium bisulfite and formaldehyde;

and

(0) sodium sulfite, sodium bisulfite and formaldehyde;

the molar ratio of formaldehyde to sulfite, bisulfite, or sulfite .plus bisulfite being 1:08 to 1.2; (ii) said cooking liquor having a pH of 10.9 to 13.7 at the start of cooking, and a chemical concentration of 230% by weight calculated as S for lignocellulosic material, and a concentration of formaldehyde of 0.7- 17% by weight; (2) said mechanically defibrating being by means of a single disc refiner; and

(C) recovering high yield pulp.

2. A process of making pulp according to claim 1, wherein the cooking treatment is carried out in liquid phase at a temperature within the range of 100 l90 C. for a time from twenty minutes to 5 hours, at a liquid ratio of 2 to 20 and in chemical concentration of 530% by weight as S0; for lignocellulosic materials.

3 A process of making pulp according to claim 1, wherein the cooking treatment is carried out invapor phase at a temperature within the range of 100-l90 C., for a time from a few minutes to one hour, at a liquid ratio of 1.0 to 4.0 and in concentration of 2 to 15% by.

weight calculated as S0 for lignocellulosic material.

4. A process of making pulp according to claim 1, wherein cooking treatment and then mechanical defibration are carried out.

5. A process of making pulp according to claim 1, wherein mechanical defibration and then cooking treatment are carried out.

References Cited S. LEON BASHORE, Primary Examiner A. L. CORBIN, Assistant Examiner US. Cl. X.R. 16228, 72, 84