SE461472B - LIGNOCELLULOSAMATER MATERIAL WITH ARCH STRUCTURE FOR TREATMENT INTEGRATION AND PROCEDURE FOR PREPARING THEREOF - Google Patents

Description

15 20 25 30 35 461 472 possible quality in the final product is required. that the pulp holds a relatively high proportion of long fibers. Suitable lignocellulosic materials for such pulps are, for example, chemical pulps made from softwood. In recent years, a variant of chemical mechanical pulp, so-called Chemithermomechanical pulp (CTMP), based on softwood, has proven particularly useful for the production of absorption products and certain types of board.

After the pulp is produced, it is taken up on a dryer to form a continuous wet-formed pulp web. It is usually a highly diluted pulp suspension that is fed to the dryer. Thus, the concentration of pulp amounts to 0.5-4% of the total weight of the pulp suspension. The pulp suspension is thickened on a wire to a dry content of 20-30% and then fed to a press section where the pulp is dewatered to a dry content of 40-50%. During pressing, the pulp web is subjected to strong pressing pressures in several steps. The thickness and density of the pulp sheet are determined by the compression pressure. After pressing, the pulp web is passed through a drying section for final drying to a dry content of 85-95%. The resulting pulp web can be rolled up on a relatively coarse shaft, a so-called drum roll to form roll mass or cut into sheets. which in stacked form form a pulp bale. Sheet or roll mass made of, for example, CTMP, has a density of 300-380 kg / m3. In the production of flake-dried pulp, the pulp web is defibrated after the press section into small flakes which are blown to a dryer with a fan. The dried flakes are pressed into plates. whose thickness can vary from approx. 10 cm up to approx. 20 cm. These tiles have a density of 600-800 kg / m3.

In the converter, which uses the mass, e.g. for the production of absorption products, the pulp disintegrates into fluff, which product can be compared to cotton wool. The disintegration is carried out in different types of hammer mills or disc refiners. For practical reasons, the converter prefers to use roll pulp. which is continuously fed into a hammer mill. The disintegrated pulp is blown to a dry forming station to form various end products, such as, for example, tissue or diapers.

From the point of view of the manufacturer and the buyer, it is desirable that the pulps used have as high a density as possible because the volume of pulp per unit weight then decreases. This is important taking into account the shipping cost and, as mentioned above, it is known to increase the density of a pulp sheet by vigorously pressing the wet pulp before drying.

Technical problem It has turned out. that heavy pressing of wet pulp results in hard sheets, which become difficult to completely disintegrate into fluff. In achieving high quality fluff, ie. with a low amount of non-decomposed material, one tries to carry out the disintegration as efficiently as possible. intensified, however, the risk of fiber shortening increases, the striving for I as the mechanical processing ie. that fibers are cut to a shorter length than the original, which lowers the quality of the fluff, gives an inappropriately high density and also deteriorates the working environment in the form of increased dust formation. The fiber shortening also leads to poorer use properties in the end product. In addition, when using diapers, poorer absorption capacity is obtained. i.e.

In addition to the mentioned problems with overpressured pulp sheets, there is also the higher electrical energy consumption required to disintegrate the pulp sheet into fluff. hardness is added to the storeability by In order to reduce the expensive chemicals of the pressed sheets, which reduce the number of hydrogen bonds, which occur between the fibers during the drying and storage of the pulp sheet. Description of the Invention Solution In the practice of the present invention, the problems described above are solved. Accordingly, the invention relates to a lignocellulosic material, belonging to pulps of the type chemical mechanical pulp, abrasive pulp or refiner pulp of low density, with sheet structure and improved properties in dry integration in a hammer mill, intended for the production of density standard method absorption material, characterized by a 40 -s7s kg / m3 SCAN-P7: 75 and a storeability calculated as electricity consumption when disintegrating the material in a hammer mill of between 30 and 60 kwh / ton pulp, preferably 35-50 kWh / ton pulp.

After disintegration, the lignocellulosic material has a bulk of 15-23 cms / g measured according to the standard method SCAN-C 33:80. and a network strength of 2.80-4.50 N. The invention also relates to a method for producing a sheet structure wet-formed pulp web, in the dry state, in connection with drying of a continuous lignocellulosic material web, the wet-pulp web first being pressed to a dry content in the range 40- 50% and within the range measured according to which is easy to disintegrate after being dried to a dry content in the range 85-95%, characterized therefrom. that the continuous wet-formed pulp web is substantially unchanged dry content at a dry content in the range 85-95% is compressed at a press pressure corresponding to a line pressure in the range 30-300 kN / m.

Preferably, the line pressure is kept within the range of 50-200 kN / m. The process results in a product with an increased density but which, in relation to the increased density, is still easy to disintegrate. The desired compaction is most easily achieved by passing the pulp web through one or made of hard material in a roller press. It is also possible for several pairs of rollers to use other pressing equipment, flexible, manufacturing of chipboard. the pulp web is treated to a higher density. for example belt presses with converging double plates, which i.a. used in In special cases, the pulp web can also with heat in connection with compaction of Regardless of the apparatus to be According to the invention used for the compaction according to the invention, the density of the pulp is increased by at least 10%. the compaction results in only a slight change in the dry content of the pulp. Thus, the increase in the dry matter content of the pulp does not exceed 2%.

Suitable density of the compressed material is 400-900 kg / ms.

After compaction of the pulp web to a higher density, it is particularly suitable to roll up the treated pulp jumbo roll. the web on a drum roller, whereby a so-called

The jumbo roll can then be rolled up and cut into smaller rolls, which are easy for the converter to handle.

The continuously compressed pulp web can also be cut into sheets. which in stacked form form a pulp bale.

Advantages In the practice of the present invention, a product of lignocellulosic material is obtained in sheet or roll form which is relatively easy to disintegrate in relation to its increased density. significantly more compact pulp bale or roller than in the prior art. This entails a lower shipping cost. The freight cost of boat transport is particularly advantageous, as this type of transport is less sensitive to weight and it is also advantageous to fill the ship with goods as efficiently as possible.

Due to the higher density, the saving 1 is obtained that when the volume is maintained, the work of the converter becomes An additional advantage is, the roll mass or on the pulp bale, by feeding the pulp to the production line less intensively, since each unit contains more mass by weight. 10 15 20 25 30 46? 472 Description of the Figures Figure 1 'shows a simple block diagram for the production of sheet and roll pulp according to the prior art, while Figure 2 is a block diagram of the method according to the invention. Figure 3 shows a block diagram of a variant of the method according to the invention.

Best embodiment In the prior art, a suspension consisting of, for example, high-yield pulp of the chemical mechanical type and water is passed to a pick-up and drying machine, shown in Figure 1. The pulp concentration amounts to 0.5-5%, ie. on 1 part mass there is 20-200 parts water. It is thus large amounts of water that must be removed in order to obtain a dry pulp web. The pulp suspension is passed from a buffer tower 1 through a conduit 2 to a headbox 3 which forms the first part of one (see Figure 1) - There are several different types of headboxes. pick-up and dryer Thus, there are simple headboxes that form a single layer of pulp. In addition, there are more sophisticated inlet and feed devices. which form several layers of pulp layer. When using such multilayer formation, it is possible to form a pulp web containing different types of pulp in each layer.

From the headbox 3, the pulp suspension is applied directly to an endless continuously operating wire section 4. speed varies from 30 m / minute up to 200 m / minute depending on the thickness of the pulp web. The speed can be increased with sheet thickness. The basis weight of the hash banana usually varies from 400 g / m2 up to 1,000 g / m2.

The wire separates water from the pulp fibers. At the end of the wire section, so much water has been removed that the pulp concentration (mk) amounts to 20-35%. To further increase the dry content of the pulp web, it is subjected to mechanical dewatering by pressing between one or more roller pairs 5-7.

VIIêIIS usually to descending 10 15 20 25 30 7 461 472 which are made of hard material. After pressing, the dry matter content has been pushed up to a level of 40-50%. thickness is determined in the subsequent thickness. However, some masses have a certain ability to try to regain a freer and more bulky shape, ie. a tendency to strive for low density. An example of a mass banana's large extent of the pressing. At a drying section 8, drying is fixed in this mass having such a mass. which gives extremely low density is a variant of high yield pulp. namely the so-called chemithermomechanical pulp (CTMP). which has a density of 300-380 kg / ms. Chemical pulp usually has a density of 500-750 kg / ma.

In the drying section 8, the pulp web is dried to a dry content of 85-95% by allowing the pulp web to pass between a number of oils or electrically. The pulp web can also be airborne and dried with cylinders, hot water, tricity. the air. stacked into bales or the pulp web is rolled up on a relatively rough shaft. s.k. tambourvals. The so-called the jumbo roll is then cut up and rolled into smaller width rolls. or with plastic film to protect the goods during transport to manufactures diapers, and the free ones which are heated with steam, the pulp web is then cut either up into sheets as bales and rolls wrapped with thick paper converter. At a converter. for example, the roll mass is placed in a special rack to which product the end of the roll is usually led hammer mill, for disintegration into fluff, can be likened to cotton wool.

Example 1 In a pulp mill, where CTMP intended for diaper making is produced, rolls of CTMP were manufactured according to known techniques.

Peroxide-bleached and water-diluted CTMP, with a freeness according to the standard method SCAN-C21: 65, of 650 ml CSF (Canadian into a line 2, (see Figure 1), a wire section 4) was passed.

Standard Freeness), to a headbox 3, after which the pulp was taken up on the pulp concentration of the pulp suspension (mk) 10 15 20 25 461 472 amounted to 1.2% in the headbox and was increased by dewatering on the wire to 26%. The pulp web was then pressed in three steps 5, 6 and 7. After the first pressing step the dry matter content became 34%, after the second pressing step 40% and after the third pressing step 44%. The hash was then dried to a dry content of 91% and rolled up on a drum roller. The resulting jumbo roll is cut into smaller and narrower rolls. Samples were taken from the jumbo roll for analysis of the pulp properties, which are summarized in Table 1.

In the practice of the present invention, in the same manner as above, t.o.m. the drying, i.e. Empty. the drying section 8. Thereafter, the dry pulp web (see Figure 2) was fed to a continuously operating press section 9,10. The press party consisted of two electoral pairs 9 resp. 10 made of steel.

The pressure on the pulp web of the respective roller pairs 9 and 10 was regulated by means of hydraulics. In the experiment, a line pressure of 80 kN / m was measured at the passage of the pulp through both the first 9 and the second pair of rollers 10. The dry content of the pulp before the passage through the roll pairs 9 and 10 was 91.1% and after the passage 91.3%. After the pressing, the pulp web was taken to a drum roller, the resulting jumbo roll was made narrower and smaller rolls for delivery to From the jumbo roll, samples were taken for analysis, the results of which are summarized in Table 1.

A comparison between the rollers showed that the rollers produced according to the invention had significantly smaller diameters produced according to known technology. several reels shown, for rewinding. By customers, e.g. converters. than the rollers Measurements that the diameter of the rollers produced according to the invention was on average approx. 25% less.

Table 1 Properties of the Hassa sheet Prior art According to gpgfinninggg _ 2 Surface weight, g / m 661 653 Thickness, nm 2.01 1.49 Density, kg / nä 328 445 10 15 20 9 461 472 As can be seen from the results, it has been possible with the method according to the invention to reduce the thickness of the pulp sheet. The effect on the density of the pulp is surprisingly large and the increase. expressed as a relative percentage. is about 35%.

Considering that the pulp web has been compressed in the dry state and at a speed of 58 m / minute, it is very good.

Rolls made in the manner described above with a width of 280 mm were transported to a diaper factory, where they were disintegrated into fluff in a hammer mill. In this case, it showed that the electrical energy consumption for the look-up work became the result is remarkable, lower for the roll mass according to the invention. Thus, the specific electrical energy consumption in the hammer mill was estimated to amount to 43 kWh / ton when disintegrating roll mass produced according to the invention, while the roll mass produced according to known technology required 58 kWh / ton. The result is very surprising in view of the fact that the fluff pulp produced according to the invention had a significantly higher density than that prepared according to the prior art.

A Of the two masses, samples were taken, which were analyzed according to the standard method SCAN-C 33:80 m.a.p.

The results have been compiled in properties that are important for absorption purposes. table 2.

Table 2 Properties of fluffed pulp Prior art According to the invention 3 Bulk cm / g 17.9 17.8 Absorption time, sec. 9.5 9.4 Absorption capacity, 9 / g 9.6 9.6 Network strength, N 3.01 3.02 10 15 20 25 30 10 461 472 The values in Table 2 are shown. that the two pulps had substantially similar properties in the production of absorption products, despite the fact that the pulp produced according to the invention had a significantly higher density and required a somewhat lower electrical energy input.

Example 2 In a further experiment in accordance with the invention, the possibility of pressing wet pulp web to a, relative to Example 1, lower dry content, after the third pressing step, i.e. lower than 44% and thereby obtain a, relative to Example 1, lower density, of the pulp before drying.

The pulp web was pressed in such a way that at the first pressing stage it obtained a dry matter content of 34%, after the second pressing stage 38% and after the third pressing stage 41%. The pulp web was then dried to a dry content of 91% and then compressed according to the invention to a higher density. This slightly modified process was found to give the same results as previous experiments according to Example 1. An exception, however, was the consumption of electrical energy when the pulp was converted to fluff. Thus, a specific electricity energy consumption was obtained which amounted to only 39 kwh / ton, ie. 19 kWh / tonne lower than with the disintegration of conventionally produced rolling stock.

Example 3 In an abrasive pulp mill, long-fiber spruce pulp obtained by such a fractionation as described in U.S. Patent No. 4,562,969 was prepared. The fractionated pulp was filled into a container and transported to the CTMP plant according to Example 2. In a conventional manner, the pulp was dissolved in a pulp (not shown in the Figure) and then diluted with water so that a pulp concentration of 1.2% was obtained.

The pulp suspension was introduced into a line 2, (see Figure 1), and then into a headbox 3 and taken up on a Vira 4. Through the dewatering of the virus, an increase in the pulp concentration (mk) was obtained to 26%. The pulp web was then pressed in three steps. After the first pressing step the dry matter content was 33%, after the second pressing step 40% and after the third pressing step 43%.

The pulp web was then dried to a dry content of 91% and rolled up on a drum roller. Samples were taken for analysis of the properties of the pulp. The results have been compiled in Table 3.

In accordance with the invention, a further experiment was made in which the pulp was pressed in three steps to a dry content of 44%. After partial drying in a drying section 8 to a dry matter content of 63%, the pulp web (see Figure 3) was fed to a continuously operating press section 9, 10 for compaction of the pulp. The press section consisted of double roller pairs made by the pressure on the pulp web of respective roller pairs. 9 and 10 In the experiment, the web was measured. steel. was regulated by means of hydraulics. a line pressure of 80 kN / m at the passage of the pulp through the first pair of rollers 9 and a line pressure of 120 kN / m at the passage through the second pair of rollers 10. No change in the dry content of the pulp could be detected. The pulp compressed according to the invention was further dried in a second drying section 11 to a dry content of 91.3%. for Then the pulp web was taken to a drum roll obtained from a drum roll, narrower and smaller rolls were produced for delivery to winding. Of customers e.g. converters.

Samples were taken from the jumbo roll for analyzes, the results of which have been compiled 1 Table 3.

A comparison between the rollers showed that the rollers produced according to the invention had a markedly smaller diameter than the rollers produced according to known technology. Seals of several rollers showed that the diameter of the rollers produced according to the invention was on average approx. 30% less.

Table 3 Properties of the Hassa sheet Prior art According to the invention Surface weight, 9 / m2 650 649 Thickness. mn 1.80 1.24 nensitez, kg / ma 361 523 10 15 20 25 12 461 472 As can be seen from the results, it has been possible in the process according to the invention to substantially reduce the thickness of the pulp sheet. The effect on the density of the pulp is surprisingly large and the density increase obtained, expressed in relative percentage, amounts to about 45%. Considering that the pulp web has been compressed in the dry state and at a speed of 58 m / minute, the result is remarkably good.

Roll masses with a width of 280 mm were transported to a factory for diaper production and disintegrated into fluff in a hammer mill. It turned out. that the electrical energy consumption for the disintegration became lower for the roll mass according to the invention. Thus, the specific electrical energy consumption was estimated to amount to 41 kwh / ton when disintegrating roll mass according to the invention, while the roll mass produced according to known technology required 56 kWh / ton. The result is very surprising against the background that the roll mass according to the invention had a significantly higher density than the roll mass according to the prior art.

Samples were taken from the fluff pulp according to the invention which were analyzed according to the standard method SCAN-C 33:80 m.a.p. absorption properties important properties. Table 4 Fluffed pulp properties Known technology According to gpfinninggn 3 Bulk cm lg 18.0 18.0 Absorption time, sec. 6.0 5.8 Absorption capacity. 9/9 10.1 10.1 Network strength, N 3.51 3.46 From the values in Table 4 it appears that there is no difference between the tested rolling masses in terms of investigated properties.

Claims (6)

10 15 20 25 13 461 472 PATENT CLAIMS associated with chemithermomechanical pulp. Lignocellulose material, pulps of the low-density abrasive or refiner pulp, having a sheet structure and improving mechanical pulp, dry disintegration properties in a hammer mill, intended for the production of absorbent materials, characterized by a density in the range 400-575 kg / m3 measured according to the standard method SCAN-P7: 75 and a storeability calculated as electrical energy output in the case of disintegration of the material in the hammer mill of between 30 and 60 kWh / tonne of pulp, preferably 35-50 kWh / tonne of pulp, and that after des integration has a bulk of 15-23 cma / g measured according to SCAN-C 33:80, the standard method and a 2.80-4.50 N. network strength of A process for producing a continuous lignocellulosic material web-wet pulp web having a sheet structure which is easy to disintegrate in the dry state, the wet-pulp web first being pressed to a dry content in the range 40-50% and then dried to a dry content in the range 85 -95%, characterized by continuous wet-formed pulp web at a dry content within it. that the interval 85-95% and at a press pressure corresponding to a line pressure in the interval 30-300 kN / m is compressed between one or more roller pairs or in a belt press whereby the density of the pulp web is increased by at least 10% while maintaining good storeability . 3. A method according to claim 3, characterized in that the line pressure is 50-200 kN / m. 10 461 472 14 Method according to one of Claims 2 to 3, characterized in that the density of the pulp with the compaction is brought to be in the range from 400 kg / ms to 50 kg / m 3. hence, Method according to one of Claims 2 to 4, characterized in that the dry matter content of the pulp is increased to a maximum. 2% when compressing the pulp to a higher density. 6. A method according to any one of claims 2-5, characterized in that the pulp is heated during or after the compaction.