DK145761B - LIGHT, ABSORBING, SIMILAR HIGH-EXPLANATED CELLULOS MASSES AND PROCEDURES FOR ITS MANUFACTURING AND USE THEREOF - Google Patents

Description

(19) DENMARK Kg

Ip (12) PROGRESSION SCRIPTURE (11) 1 ((- 5761 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 5106/76 (51) Int.CI.3 D 21 C 3/06 (22) Filing Date 12 Nov. I976 (24) Race day Nov 12 1976 (41) Aim. accessed May 14, 1977 (44) Presented 21. February 1985 (86) International application no.

(86) International filing day (85) Continuation day - (62) Master application no. -

(30) Priority 15 Nov. 1975 * 7512777 * SE

(71) Applicant MO AND DQMSJOE AE, ε-891 01 Oernskoeldsvik 1, SE.

(72) Inventor Jonas Arne Ingvar Lindahl, SE.

(74) Clerk of the Office of Industrial Excellence v. Svend Schønning.

(54) Light, absorbent, lignin-rich high = yield cellulose pulp and method of preparation and use thereof.

The present invention relates to a light, absorbent, lignin-rich high-yield cellulose pulp, low resin content, low bulk weight and good absorbent properties for liquid, and improved stability against layering. The invention also relates to a process for producing in high yield such a mass from lignocellulosic material such as wood, bagasse or straw. The invention relates finally to the use of the pulp in admixture with the chemical pulp. The pulp is particularly suitable for the production of such absorbent products as soft paper of various species, cellu-D loose wadding, diapers, women's tapes and tampons.

^ For the manufacture of such absorption products, only chemical masses such as sulphite and sulphate masses are presently used. However, in the manufacture of these masses, almost half of the fiber of the wood is recovered, which is a considerable disadvantage in view of 2 145761 If the wood raw material is to be utilized more efficiently, both the mass yield must be increased and the fibers recycled, however, the recovery of hygiene paper has proved difficult to achieve economically, so that more complete utilization of the limited fiber raw material remains the only possibility. In making the so-called high-yield mass, wooden rods are abraded against a rotating rock, or the wood is first disintegrated into smaller pieces which are then fed into a disc refiner with one or two rotating discs facing grooves facing each other, thereby the wood fibers are exposed under the passage of the small pieces of wood (which could be called woodcuts) between the notarial archives. In a special development of the wood-cutter refiner process, the cuts are preheated with steam before being fed to the disc refiner, thereby preheating the lignin in the wood in such a way as to facilitate fiber deposition. This so-called thermomechanical pulp gets a higher proportion of long fibers than is achieved by the rough-or-grit or stone grinding. However, the mentioned processes have the disadvantage of having a high energy consumption. It is also known, prior to defibration, to partially delignify the lignocellulosic material with high temperature sulfur-containing compounds (above 160 ° C) and thus achieve high mass yield. By regulating the opening conditions, mass yields which vary between 60 and 93% (so-called chemical mechanical mass) can be obtained. The chemical-mechanical pulping process results in substantially lower energy consumption than that used for the production of mechanical masses of the above-mentioned type, but it has the disadvantage that it requires considerable quantities of sulfur-containing chemicals, which necessitate a costly chemical recovery plant. Another disadvantage of this method is the release of large amounts of organic matter that must be handled and treated to avoid environmental damage. Also, in the manufacture of unbleached and cured mechanical masses, a waste is obtained which must be cleaned before it can be discharged.

A common disadvantage of all the above-described mass-making processes is also that the masses must be screened in various costly and space-consuming apparatus for separating coarser particles or for enriching first-class fibers. Where screening is carried out at very low concentrations of the fibrous material, only low concentrations of chemicals and dissolved organic matter are obtained in the filtrate, which makes recovery and purification difficult to carry out and economically unattractive.

A further disadvantage associated with the known high yield masses is that they layer during transport and storage in such a way that the volume decreases greatly.

It is an object of the present invention to provide a cellulose pulp of the type initially mentioned which is clearly superior to previously known cellulose pulp for absorption purposes and furthermore has much lower manufacturing costs due to low throughput and low energy consumption.

This is achieved according to the invention at a content of 0.1 to 1.0% by weight of sulfur present in the form of lignin-bonded bisulfite and sulfate ions, an amount of retained fibers of more than 25% at the mesh size of 833 µ by a fiber grouping analysis, an amount of fiber clippers consisting of 2 -4 single fibers of at least 10%, an amount of dichloromethane extractable resin of less than 0.8%, and a bulk weight 3 in dry fiber form of less than 50 kg / m.

The pulp according to the invention preferably has a sulfur content of 0.2-0.6% present in the form of lignin-bonded bisulfite and sulfate ions, an amount of retained fibers of 35-65% by fiber group analysis at mesh size 833, u, an amount of fiber clippings consisting of 2- 4 single fibers of 15-30% and a bulk weight in dry fibrous form less than 40 kg / m.

In addition, it is particularly advantageous if the pulp of the invention has a pH of the dried pulp greater than 6, preferably between 7 and 10, whereby acidic products in the liquid to be absorbed are neutralized resulting in reduced skin irritation.

The invention also relates to a process of the kind specified in the preamble of claim 4 for the preparation of the high yield mass of the present invention, and the process is characterized by the characterizing part of claim 4.

The invention further relates to the use of the high yield cellulose pulp as claimed in claims 1-3 in admixture with chemical pulp, and this use is characterized by the characterizing part of claim 12.

145761 4

Suitable digestion chemicals for use in the process of the invention are bisulfites and / or sulfites of sodium, potassium, ammonium, calcium or magnesium, and among them sodium bisulfite or sodium sulfite is particularly preferred. The content of opening chemicals in the opening fluid must not exceed 20 g SC> 2 per liter. The pH of the impregnation of the cellulose material should be between 5 and 11, preferably between 6 and 9, and the impregnation should be carried out in such a way that 0.9 to 1.5 liters of solution are absorbed in kg of dry fiber material (dry cuts). The temperature used during the opening should be lower than normal in the preparation of the chemical mechanical mass in order to obtain the appropriate partial opening according to the invention to the appropriate degree of sulfonation. Suitable temperatures for this are 373-443 K, preferably 383-403 K. It is convenient during the impregnation to maintain the same temperature as during the opening, and particularly preferably to steam the water bath washed sections during the impregnation.

The partial opening according to the invention is essential to obtain the advantageous properties of the product. Hereby the lignin contained in the lignocellulosic material is softened and some of it is sulfonated so that it can be released later. A suitable degree of sulfonation is 0.1-1.0%, preferably 0.2-0.6% sulfur, based on the weight of the treated lignocellulosic material. Different types of wood require different opening conditions within the foregoing framework to achieve the above-mentioned sulfonation degree. Most importantly, the opening is performed in such a way that no free or bound sulfur dioxide is present in the opening fluid after the partial opening is completed. For this reason, residence time • 3 »__ 5 14576 1 and temperature must be adjusted accordingly. A suitable residence time in the impregnation step is 0.5-5 minutes and a suitable residence time in the opening step is 0.5-30 minutes, preferably 2-10 minutes.

After the partial opening, according to the invention, the mass obtained is defibrated mechanically in a defibrillation insert in an incomplete manner and so that the defibrated mass will contain at least 10% fiber bundles. By fiber bundles is meant here thin fiber bundles containing 2-4 single fibers. In contrast, hard fiber bundles containing unsulfonated at or fiber bundles with 5 or more single fibers (so-called laces) are not aimed. Preferably, the partial mechanical defibration is carried out in such a way that the defibrated material will contain at least 15-30% fiber clippings of the kind specified above. The partial mechanical defibration must therefore be carried out in such a way that any form of fiber shortening during defibration is avoided, which can be achieved by treatment in high-consistency mills. By performing the partial mechanical defibration in the manner described above in combination with the partial opening, a particular suitability of the finished product for use for absorption purposes such as low room weight good water absorption, including absorption rate and retention capacity, good storage resistance under storage conditions is achieved. low resin content and good brightness.

In the partial mechanical defibration, according to the invention, resin removal and bleaching chemicals are present. Suitable resin removal chemicals are phosphates, complexing agents and / or surfactants, and phosphates are particularly preferred and resin removal is carried out in an alkaline environment, with alkali metal hydroxides such as sodium hydroxide being particularly preferred. The pH of the resin removal fluid supplied to the defibrillation plant should be above 11 in order for the initial pH of the pulp suspension to be above 9 and preferably be maintained above 10, which is convenient according to the invention. Suitable bleaching chemicals for application to the defibrillator at the same time as the resin removal chemicals are alkali metal peroxides such as sodium peroxide or hydrogen peroxide, but also so-called reducing bleaches such as ditionite, hydroxylamine, thiourea or thioglycolic acid may be available. Other oxidizing bleaching agents such as ozone, persulfates, gaseous oxygen, peracetic acid and borax may also be considered as bleaching agents in the present process. The defibration results in homogeneous mixing of added chemicals and a faster effective saponification of fatty acids and resin acids, which facilitates the dispersion of unsaponifiable parts of the extractants. To these reactions also contributes the relatively high temperature and the intensive mechanical machining.

After the partial defibration, according to the invention, it is convenient to dewater the obtained pulp suspension to a dry matter content of at least 30%, preferably to 45-55%, at high temperature, preferably above 348 K. The high temperature results in the best possible separation of saponified and dispersed extractives and high solids content of the pulp to be subsequently dried. In addition, dewatering means that chemicals and dissolved organic matter to be collected are in a high concentration.

One apparent advantage of using the present method is that the fiber yield becomes very high, namely between 85 and 95% and preferably between 90 and 94%. In addition, the process results in very low energy consumption, namely between 200 and 1100 kWh per year. tons of dry cellulose fibers produced. The process according to the invention also has the advantage that the volume of the excess excess liquid from the process becomes small and concentrated in terms of contaminants, and that the collection of liquid can take place in a single place. This makes it possible to recover useful chemicals in a simple and economical way and / or purify the process return water. It is also important that the apparatus used only requires low investment costs because the cellulose material does not need to be screened, which further reduces energy consumption.

A further advantage of the present process is that the heat generated during the process can be easily collected and recovered. The process thus produces low-pressure steam, which can be utilized, for example, by evaporation or for district heating. A further advantage of the present process is that water consumption 3 becomes extremely low, namely approx. 3 m water per tons of dried cellulose material produced. Corresponding figures in the preparation of chemical 3 mass are approx. 250 m and at a mechanical or thermomechanical mass approx. 20 m ^.

As raw material in the process according to the invention, lignocellulosic material such as wood, bagasse and straw are used. Particularly suitable is the use of wood fibers, which may also include some admixture of recycled fibers. When using fresh or stored wood, sticks are first chopped up in a comminution machine, after which the formed pieces are washed in warm water. At the same time, iron objects are separated by means of electromagnets, which can otherwise damage moving parts of the machines. Particularly sensitive to this is the defibration apparatus used in the process.

In a particularly preferred embodiment of the method according to the invention, which can be carried out in an apparatus as shown in the drawing, in a wood washer 1 well washed and hot comminuted wood is transported to a heating vessel 2 where it is treated with saturated steam at atmospheric pressure. This step in the process is called steam heating and aims to drive air out of the finely divided wood and to level the water content. After the steam heating, the finely divided wood is fed into a screw conveyor 3 which opens into an impregnation chamber 5. The washed, finely divided wood can also be fed directly into the screw conveyor 3, ie. that in this variant there is no steam heating. At the passage of the finely divided wood through the screw conveyor 3, it is compressed in such a way that excess liquid flows out through a drain outlet 4 in the screw conveyor. Once the finely divided wood has passed the screw conveyor 3, it is allowed to freely expand in the impregnation chamber 5. The impregnation chamber 5 is filled with a weak solution of a disulfite and / or sulfite of Na, K, NH4, Ca or Mg. It is particularly convenient to use sodium bisulfite or sodium sulfite. In order to achieve rapid sulfonation of the lignin during the treatment in the impregnation chamber and in a boiler, the pH value of the impregnating solution must be between 5 and 11 and preferably between 6 and 9. The total content of chemicals in the impregnating solution, expressed as sulfur dioxide, amounts to a maximum of 20 g SC > 2 pr. liter. From the free expansion of the finely divided wood in the solution, it has been experienced from experience that for every kg of calculated wood solids 0.9-1.5 liters of solution are absorbed. The volume of solution absorbed varies with the nature of the tree. Inside the impregnation chamber are two vertical screws 6 and 7 which transport the finely divided wood upwards to the upper end of the chamber. In order to obtain a homogeneous impregnation and to obtain a liquid phase partial sulphonation, the finely divided wood is hereby transported slowly upwards in the impregnation chamber. At the same time, the liquid level in the impregnation chamber is kept as high as possible. This is done automatically by means of sensors and control valves which are not shown in the drawing. The treatment in the impregnation chamber is most conveniently carried out according to the invention at a temperature of 373-443 K., preferably 383-403 K, for a period of 1/2 to 5 minutes. From the upper part of the chamber, the finely divided tree falls into a lower-lying boiler 10.

The finely divided wood leaving the impregnation chamber 5 has a dry matter content of approx. 35%. In boiler 10, the finely divided wood is partially sulfonated at a temperature of 373-443 K, preferably at 383-403 K.

The indicated temperatures also prevail in the impregnation chamber 5 because this part is in connection with the boiler part 10. The heating in the boiler part takes place by supplying saturated steam through a connection 8, ie. that the continued sulfonation of the wood is carried out in the vapor phase. The residence time in the boiler part is usually 1 / 2-30 minutes. It has been particularly convenient to use a residence time of 2-10 minutes. According to the invention, the residence time and temperature are to be controlled in such a way that no free or bound SO2 can be detected in the opening liquid in the lower part of the boiler from which the partially sulfonated comminuted wood is transported out. This is essential to prevent the reduction and degradation of the peroxide solution used as a bleach as well as to avoid the formation of sulfuric acid which gives rise to the extraction of extractants on the fibers of the pulp, which affects the brightness and absorbency of the finished product.

The partially sulfonated comminuted wood is then removed from the boiler by means of a transport screw 12. A preferred embodiment of the method is conveying the screw the finely divided wood to a disc refiner 13 or other defibrating means, e.g., a high concentration treatment screw vibrator which provides a kneading effect and shear without breaking the fibers. Apparatus of the latter type are traded under the trademark "FROTAPULPER" which is not registered in Denmark. The mechanical defibration is carried out under a pressure equal to or slightly lower than that prevailing within the cooker. In addition, it is essential in the process that the cellulose material is mechanically defibrated only partially, i.e. that the pulp after defibration 145761 9 should contain fiber bundles consisting of 2-4 single fibers, which is very advantageous for the outcome of the finished product. The partial mechanical defibration is carried out in such a way that the defibrated mass after defibration contains at least 10% and according to the invention preferably 15-30% such fiber bundles. In addition, any fiber shortening during defibration must be avoided, which is also achieved by treatment in high-consistency type disc refiner mills or one of the aforementioned appliances traded under the trade name "FROTAPULPER". Partial sulfonation also avoids the formation of hard fiber bundles, and also named splices, which are always formed by the production of mechanical pulp in an amount greater than 2% of the total amount of fiber material.

Resin removal and bleaching chemicals, preferably according to the invention, as set forth in claim 7, are applied before defibrillator 13 via a connection 11 to the supply screw 12. The addition of resin removal agents, e.g., Na 2 PO 2, may vary between 0.1 and 1. 5% by mass. Preferably, 0.2-0.4% is used. The amount of surfactants should be maximized to 0.2%, while the amount of complexing agents such as NTA, EDTA and DTPA should be at most 0.3% of the mass of the mass. When hydrogen peroxide is added, at least 4% of the weight of the mass is added and preferably 1.0-2.0%. The sodium hydroxide content must be at least 65% of the peroxide addition and not more than 200% of the peroxide addition. In addition, to stabilize the peroxide, 0.5-4.0% sodium silicate and / or 0.05-0.5% magnesium sulfate can be added. When recovering chemicals from the process water, the addition of sodium silicate must not exceed 0.5%. The defibrated cellulose material is then blown through line 14 to a cyclone 15 to separate low pressure vapor 17 from the cellulose fibers. The cyclone is provided with valves 16 for regulating the steam outlet and for regulating the pressure of the steam. In addition, the cyclone is directly mounted together with a press 18 in which the mass exiting from the cyclone is collected and dewatered. From the cyclone, steam 17 is withdrawn, the pressure of which is somewhat below the pressure in the disc refiner's paint house. The exhaust steam can be used for various purposes, for example for heating rooms or evaporation of chemical-containing liquids. In the press 18 14576! The defibrated dry cell holding cellulose material is dewatered. at least 30%, preferably 45-55%, at high temperature. The liquid from the press contains chemicals and released organic matter which is conveniently collected via the effluent 19 by evaporation, separation of extractive substances and burning or otherwise collection of the chemical content. Since the defibration is carried out at a mass concentration between 20% and 40%, only a small volume of excess liquid is obtained. The mass concentration decreases during treatment in the refiner because sealing water must be supplied.

After passing through the cyclone and the press, the bulk material can be made to pass an additional cyclone or press for separating steam or to increase the dry matter content of the pulp according to the invention suitably as claimed in claim 8.

According to the invention, the cellulose material, after dewatering, is fed directly to the drying plant without further intermediate treatment, where the dewatered pulp according to the invention can be dried to a dry matter content of at least 86%, preferably 88-92%. The drying system may consist of a dryer with metal wire screen and rollers or a flock dryer. However, in the former case, the cellulose material must first be diluted to appropriate concentration with recirculating liquid.

According to the invention, the partial mechanical defibration is conveniently carried out at an initial pH of above 9, preferably above 10.

However, the partially sulfonated material may also be fed directly from the digester to a pressure cyclone and then defined by the addition of bleaching and resin removal chemicals and extruders. In addition, liquid phase boiling can be used instead of steam phase boiling.

. The ratio of the proportion of long-fiber material in the mass produced by the process according to the invention to the thermomechanical mass produced in a normal manner with a 240 ml freeness according to Canadian Standard Freeness is shown in the fiber grouping analysis below in a Bauer Mc Nett apparatus.

145761 11

Mesh size Mass according to the invention Thermomechanical mass

Detained Released i- Detained Released _______% _ through% _% _ through% 833 u 40 60 10 90 104 µ 43 12 60 30

Thus, the mass produced by the process according to the invention contains approx. 4 times as much long-fiber material as the thermomechanical mass, approaching the fiber composition of chemical mass. Surprisingly, as will be shown below, the rate of absorption and ability to retain absorbed water of the mass produced by the process of the invention is excellent despite a relatively high freeness of approx.

450 ml, according to Canadian Standard Freeness. Furthermore, the long fiber of the mass produced by the process according to the invention results in a significantly better storage stability of absorption products made therefrom than of absorption products made of thermomechanical mass. The latter contains such a high proportion of short fibers that, when used in absorbent products, it settles into layers during the storage time, thereby rendering the product unusable for its purpose.

As can be seen from the samples explained below, the pulp produced by the process according to the invention is extremely suitable as an absorbent material in diaper, ladybird, tampon and dressing material products. Due to the low resin content, the pulp can also be further processed to be used as a pulp. In the tests, as reference masses, whole bleached sulfite mass, peroxide bleached stone abrasive mass and peroxide bleached thermomechanical mass were used. The reference masses were dried to a dry matter content of 94% and then conditioned in such a way that the moisture content after 10 days was 10%. The samples were then dried (so-called fluffing) in a disc refiner with disc diameter 300 mm. The fluffy masses were then tested for water absorption and volume. In the analysis, the following method was used. Test pads with a diameter of 500 mm and a weight of 2.00 g of fluffy mass were ground in a separate apparatus. By loading the sample with 100 g and then measuring its thickness, a measure of room weight was obtained. The thickness of the sample was fixed to 15 mm and then allowed to absorb water at a temperature of 293 ° K from below, measuring the absorption time. The absorption capacity was then determined at a load of 1000 g.

The results of tests on the reference masses are shown in Table 1.

Table 1

Reference mass testing.

Yield Extraction Lightness Volume Absorption Absorption% hold, di-% SCAN, 3 tion, chloromethane, hast., G H ^ O / g _% _ sec. lot

Sulfite mass 52 0.40 92 36 26 10.9

Abrasive mass 96 1.05 72 67 19 10.7

Thermomechanical Mass 95 1.02 71 59 9 10.9

A low room weight and a short absorption time are criteria that the fluffy mass is a good starting material for eg diapers. As can be seen in Table 1, the sulfite mass has low bulk but an advantage. relatively long absorption time. The abrasive has too high room weight and relatively low absorption time. Thermomechanical mass has high room weight but short absorption time. The ability to retain absorbed water is approximately equal in samples and can be considered to be at a fully acceptable level. The method according to the invention is illustrated by some embodiments.

145761 13

Example 1

Two masses, A and B, were prepared, of which Sample B was treated in accordance with the present invention. Granwood was cut into wood chips with a length of 30-50 mm, a width of 10-20 mm and a thickness of 1-2 mm in a chip chopper. The sections were washed in warm water and placed in a steam heating vessel, where they were treated with saturated steam at atmospheric pressure for 10 minutes. The steam heated sections were transported with a screw conveyor to an impregnation chamber. The impregnation chamber was filled with a sulfite solution having a pH of 7.5. The content of SC> 2 was 5 g / liter and the content of NaOH 6.5 g / liter. In impregnation, the sections absorbed an average of 1.1 liters of sulfite solution per day. Thus, the content of absorbed SC> 2 was 1.1 x 5 = 5.5 g per kg. kg of chips or 0.55%. The temperature in the impregnation chamber was kept at 398 K. The total residence time of the impregnation chamber was approx. 2 minutes. During this residence time, weak sulfonation of the wood material was obtained in liquid phase. The impregnated shavings were fed to a boiler where saturated steam was supplied in such a way as to obtain a temperature of 398 K. The residence time of the cutters was 4 minutes. Thus, the residence time that was in the impregnation chamber, the total sulfonation time was 2 + 4 = 6 minutes. From the bottom of the boiler, the cuts were carried with a conveying screw to a disc refiner under steam pressure of 150 kPa overpressure (1.5 ato).

In the disc refiner, the sections were partially defibrated, ie.

that a certain proportion of fiber bundles consisting of 2-4 fibers could be detected after the defibration. The solids content in the center of the disc refiner was 30%, while the mass concentration at the periphery of the discs was 35%. Energy use for defibration was measured at 750 kWh per hour. tonnes produced mass calculated as dry mass. At the exit from the refiner's paint house, the pulp was diluted with sealing water to a mass concentration of 27%. The defibrated pulp is blown to a pressurized cyclone to separate excess vapor from the pulp fibers. The pulp fibers were collected in a press mounted with the cyclone. In the press, dewatering of the pulp occurred from 27% pulp concentration to a pulp concentration of 42% at a temperature of 363 K. The amount of pulped pulp was thus, about -3 3 calculated to m per m. tons of dry mass, only 1.3 m. The content of organic matter in the solution was 60 kg or 46 g / liter, while free or bound sulfur dioxide could not be measured. The mass yield was 94%. The stock with the dry matter content of 42% was dried in a flake dryer to a dry matter content of 94%, conditioned and dried, and tested in the same way as the reference masses above. The mass thus treated is called Sample A.

In another experiment in accordance with the preparation of Sample A, resin removal and bleaching chemicals were added to the center of the defibrillator grinding discs as set forth below, and the following chemicals were added (the amounts being expressed as 100% chemicals in% of the dry mass): 0.1% EDTA (ethylenediaminetetraacetic acid) 0.3% NacP 01Λ 5 3 λ 0.05% "BEROCELL-25" (wetting agent) 1 2.0% H2O2

1.8% NaOH

2.0% sodium silicate (water glass), 40 ° Bé X1 J "BEROCELL" is a trademark registered in Denmark.

After defibration and weighing in accordance with Preparation of Sample A, the pulp designated Sample B was dried as described above and tested as the reference sample and sample A. The results are shown in Table 2.

Table 2

Testing of sample masses A and B.

Yield Extract-lightness Volume Absorption-Absorption% hold, di-% SCAN., 3 tion, chloromethane, hast., G H2 O / g __% _ sec. lot

Sample A 94 1.52 59 32 100 5.2

Sample B 94 0.58 71 33 8 11.3

As can be seen from Table 2, both Sample A and Sample B have a surprisingly low compartment weight that is much lower than the compartment weight of the sulfite mass (see Table 1). Compared to the mechanical masses, the masses produced in accordance with the invention have half the space weight. However, despite the sample being partially sulfonated, sample A exhibits very poor water absorption.

146761

On the other hand, after the addition of bleaching and resin removal chemicals in accordance with the present invention, a surprisingly good absorption rate and good ability to retain absorbed water have been obtained and the mass produced according to the invention (Sample B) is therefore quite superior to the reference masses and sample. A as absorption material in absorption products.

By comparison with the wood consumption and energy consumption of the conventional masses, significant advantages are seen in the process of the present invention.

Wood consumption and energy consumption for the production of 1 ton of mass calculated as dry mass._

Yield% At m ^ solid kWh Sulfite mass 52 5.01 800

Abrasive Mass 96 2.71 1400

Thermomechanical Mass 95 2.84 2100

Sample B 94 2.77 750

Thus, the process according to the invention provides minimal energy consumption while low wood consumption.

In addition, considering the lower investment costs of producing the pulp of the invention by eliminating the screen mill, it is clear that the process of the present invention involves producing a high solder mass for absorption products at substantially lower cost than previously possible, at the same time. by reducing the release of environmentally damaging substances by improving the conditions to provide high purification of what is discharged.

Claims (4)

16 145761 1. Light, absorbent, lignin-rich high-yield cellulose pulp, low resin content, low bulk weight and good absorption properties for liquids, and improved layer stability, characterized by a content of 0.1-1.0% by weight of sulfur present in the form of lignin-bound bisulfite and sulphite ions, an amount of retained fiber exceeding 25% by fiber group analysis at mesh size 833 microns, an amount of fiber cutters consisting of 2-4 single fibers of at least 10%, an amount of dichloromethane extractable resin of less than 0.8%, and a 3 room weight in dry fiber. shape below 50 kg / m. High yield mass according to claim 1, characterized by a sulfur content of 0.2-0.6% present in the form of lignin-bound bisulphite and sulphite ions. an amount of retained fibers of 35-65% by fiber grouping analysis at mesh size 833 microns, a quantity of fiber cutters consisting of 2-4 single fibers of 15-30% and a bulk weight in dry fiber-fiber form of less than 40 kg / m3. High yield mass according to claims 1-2, characterized in that the pH of the dried mass is above 6, preferably 7-10. 4. A process for producing a light, low absorbent high yield mass and good absorption properties as claimed in claims 1-3, wherein the process is fresh or stored wood cuts washed with water, pressed, impregnated with a sulfur-containing opening chemical, partially dissolved at elevated temperature. and then defibrated mechanically and bleached, characterized by a) that the content of the impregnating fluid of the opening chemical is a maximum of 20 grams of SO and the pH of the impregnating liquid is maintained at 5-11, preferably 6-9, b) the partial immersion is carried out to a degree of sulfonation corresponding to 0.1-1.0, preferably 0.2-0.6% sulfur bound in the form of lignosulfonates. , calculated on the dry weight of the treated cellulosic material, at a temperature of 373-443 K, preferably 383-403 K for a period of 0.5-30 minutes and in such a way that the closing liquid at the end of the opening contains no free or bound SC> 2