FI69323B - FOERFARANDE FOER FRAMSTAELLNING AV FOER VIDAREBEARBETNING TILLABSORPTIONSPRODUKTER LAEMPLIGT UTGAONGSMATERIAL - Google Patents

Description

1 69323

A process for the preparation of a starting material suitable for further processing into absorption products

The invention relates to a process for processing web-dried pulps for the production of absorption products. Pulp means pulp such as chemical, chemimechanical and mechanical pulps. Examples of such pulps are sulphite and sulphate pulps, plate refiner and pulverized pulps. The invention is thus suitable for practical! considering for all types of web-dried pulps.

In the manufacture of absorption products, large quantities of pulp fibers made from various ligno-cellulosic materials are used. These are well interlocked in 15 sheet form in the form of bales or rolls. The sheets in the bales are usually 400-800 mm long, 2 3 300-800 mm wide, 600-900 g / m square and 700-900 kg / m (bale). The rolls in principle comprise extremely long pulp sheets cut to widths which usually vary between 100 mm and 150 mm (in roll mass 3) with a density of 600-750 kg / m 2. It is also known to be used as a raw material for the manufacture of absorption products in soil which has been torn into flakes (flake mass) before drying. The dry matter content of the flakes before drying is about 50%. After drying the flakes to a dry matter content of 85-92%, they are compressed into decimeter-thick sheets which, due to the fact that hemicellulose acts as an adhesive, are very hard and difficult to break down and have a density of the order of 550-800 kg / m 3. The flake pulp also contains a large number of fiber nodules. Flake-dried sheets are supplied in the form of bales, the height of which can vary from 300 mm to 1200 mm.

In the manufacture of absorption products, the roll pulp or bale pulp is shredded and defibered to obtain a bulky pulp of 35. One problem with fiberizing bale pulp is that it is difficult to obtain uniform production. It is still difficult to obtain a uniform dry matter content due to the fact that the bales consist of relatively large individual parts in the form of sheets or sheets. When handling ordinary 5 bales, strong tearing equipment is required, which requires a certain minimum production to work well. Manufacturers of relatively small absorption products are thus reluctant to be able to use bale pulp but have to resort to more expensive roll pulp. In addition to the need for minimum production for shredders, the investment costs become unrealistically high for those manufacturers who use a relatively small amount of bale mass.

Roller pulp handling uses simpler shredders than tearing the bale pulp. Technically, the roll mass 15 works relatively well. However, one disadvantage of roll pulp is that it is expensive to manufacture in a pulp mill, due to the fact that it requires a longer drying time so that it does not become too hard. Roll pulp requires a market price that is $ 100 per tonne higher than the price of bale pulp.

The problems described above are solved by the present invention.

Accordingly, the invention relates to a process for the preparation of a starting material which is suitable for further processing into absorption products, in which case web-dried pulps are used as raw materials.

The method is characterized in that the dried pulp, closely connected to a web dryer in a pulp mill, is broken up into flakes and the obtained flakes are compressed into larger, easily handled and transportable units with a spreading density of 200-800 kg / m 3, preferably 300-700 kg / m 3.

The flakes obtained are then compressed into larger units already at the pulp mill in order to convert them into a form suitable for transport to the conversion plant and easy to handle.

35 It has further proved particularly advantageous that the dry matter content of the web-dried pulp is at least

II

3 69323 80% before disintegration, which is preferably carried out by tearing so that at least 70% of the mass after tearing is in the form of pieces with a diameter or length and width varying between 2 mm and 70 mm, preferably between 5 mm and 40 mm. The remaining parts of the pulp get sizes from outside this range. Prior to the production of the absorption products in the conversion plant, the flake-containing units thus prepared are torn and fiberized in a known manner by known devices. Due to the good pulping properties of the starting material 10 according to the invention, tearing can then take place considerably more easily than with known bale masses.

In applying the method according to the invention, it has proved advantageous to cut the web-dried pulp pulp into flakes in a mill, which are loosely stacked on top of each other, after which the sheet stack is cut into strips, which in turn are broken into flakes which are then compressed to form larger units. Alternatively, the web-dried pulp 20 directly after the web dryer, without being cut into sheets, can be broken up into flakes, which are then compressed to form larger units. The latter option is advantageous in that it allows equipment to be saved for making sheets and for stacking and cutting them.

The invention provides considerable energy savings compared to what is required in the conventional conversion of bale mass to shredded mass. It is further possible to eliminate the conventional fabrication of sheets and their compression in a pulp mill and instead, by means of a simple spike roll, to convert the dried pulp web into flakes, which are then compressed into larger, easily transportable units of the desired density. The higher cohesiveness of the starting material prepared according to the invention further causes a reduced consumption of wood raw material. The invention also makes it possible for small manufacturers of absorption products to switch to cheaper mass use as a starting material and, in addition, to eliminate certain equipment, such as guillotines and strong-type rippers.

The invention is illustrated by the following exemplary embodiments, which represent preferred embodiments and are each compared in a series of experiments according to conventional techniques.

Example 1 10 In a sulphite mill in which spruce was made into a 2-stage pulped fully bleached sulphite pulp with a viscosity of 110 cm / g and an ISO brightness of 93%, an apparatus for cutting pulp sheet bales into strips was installed after the dryer. guillotine. In this case, the sheets 15 were loosely stacked on top of each other without compression, after which they were cut into strips with a guillotine. The strips were 5 cm wide and 80 cm long. The dry matter content of the pulp immediately after the web dryer was 93%. The pulp strips were conveyed by a belt conveyor to a hammer mill, where the strips 20 were reduced to flakes having a mean length of about 20 mm and a mean width of about 15 mm. The pulp flakes were transferred to a plate press and then to a bale press. In the experiment, larger units were made in the form of bales weighing 180 kg of dry mass. The bales with sides 25 straight were 47 cm high, 91 cm long and 3 65 cm wide. This gave each bale a density of 650 kg / m. After two weeks of conditioning, the flake bales were transported to a conversion plant to make baby diapers. Their dry matter content was 91.5%. In this factory, bales containing hiu-30 bales were opened and torn into small pieces using a simple stick ripper. The size and number of these became the same as the flakes obtained before roasting at the pulp mill. The pulp flakes were transferred to a transport screw-wool plate mill as a fibrous shredded pulp. In experiments-35 sa it could be found that the flake bales were easy to tear apart and easy to defiber the pulp. Furthermore, it was found that the damage caused by static electricity was significantly lower than normal. At the test, diapers weighing about 32 g were made. The weight distribution of the diapers was -1 g and was completely satisfactory. Pulp lift and suction-5 females were checked before diapers were made. The result is given in Table 1 below.

For comparison, a sheet pulp was taken from the factory and stacked and compressed into bales in the same manner as mentioned above. The bales weighed 190 kg 3 10 (dry) and had a density of 685 kg / m. The pulp dry matter content immediately after the web dryer was 93%. After two weeks of conditioning, the dry matter content was 92.0%. The pulp bales were then transported to a convection plant where they were broken up into strips with a guillotine.

15 The strips were 5 cm wide and 80 cm long. The pulp pellets were conveyed by a belt conveyor to a hammer mill where they were comminuted into flakes with a mean length of about 20 mm and a mean width of about 15 mm. The pulp flakes were conveyed by transport screws to a disc mill for defibering. No difficulties were observed in making the sheaths from the fiberized pulp, except for certain problems caused by static electricity. At the test, diapers weighing about 32 g were made. The scatter in the diaper weight was -1.

The cohesiveness and absorbency of the pulp were checked immediately after 25 defibering, i.e. just before the diapers were made. The results are given in the following table. All measurements and performed according to SCAN-C 33:80.

Table 1 30 Comparative experiment Invention of total energy consumption for tearing and defibering, kWH / ton of pulp 71 63 cohesiveness, (bulk), m 2 / kg 18 20 suction speed, s 6.0 5.5 35 suction power, g H 2 O / g pulp 10.0 10.5 69323

As can be seen from the table, the method according to the invention has surprisingly consumed less energy than the conventional method. No definite explanation can be given for this surprising result, but one possible theory may be that weaker and thus fewer fiber-fiber bonds are formed between the flakes during storage in the flake-containing bale units made according to the invention. It is further shown from the table that the consistency of the pulp produced according to the invention is higher, which makes it possible to produce products with a constant volume but using a smaller amount of weight than pulp, i.e. pulp and thus wood raw material can be saved. Another surprising and positive effect is that the suction power of the pulp has not deteriorated, due to the fact that there is a smaller number of fibers per unit volume. Good suction rate is still maintained.

Example 2

In the same factory as in Example 1, 25% flake-dried spruce ground with 300 freeness CSF of 300 ml and bleached with hydrogen peroxide to 73% iso-brightness was mixed into the sulphite pulp. The ground pulp was converted to a 3% pulp in a pulper, which was diluted and passed to the headbox of the collecting machine at the same time as the sulphite mass, after which the mixed mass was dried on a collecting machine to a dry matter content of 93%. The resulting pulp sheets were loosely stacked on top of each other without compression and cut into guillotine strips, shredded into flakes in a hammer mill, and compressed into larger units in the form of bales with straight sides in the same manner as in Example 1.

By mixing 25% of the groundwood, the weight of the bales was reduced to 150 kg of the dry mass and the average density of the bales was 528 kg / m3. The bales were stored for air conditioning for two weeks to equalize the moisture content. The bales were then transported to a conversion plant where a jacket was prepared in the same manner as described in Example 1. Samples were taken to measure brightness, cohesiveness, absorbent properties and average weight of diapers. The results are summarized in the following Table 2, which also shows the total energy consumption for tearing and defibering.

5 For comparison, an experiment was performed using a conventional technique. The same sulphite pulp was used as before, mixed with 25% peroxide-bleached spruce, flake-dried to 90% dry matter and in the form of bales containing five plates of 9 cm each. While mixing, one plate of ground pulp was stacked on each bale of sulfite pulp. The mixed bale was then cut with a guillotine into 5 x 80 cm strips, which were conveyed by a belt conveyor to a hammer mill where they were reduced to flakes with a mean length of 20 mm and a mean width of 15 mm. The flakes were conveyed by a screw conveyor to a plate mill where they were defibered into a shredded pulp.

Samples were taken and analyzed as above. The results obtained are shown in Table 2 below.

^ Table 2

Comparative test Invention total energy consumption, kWh / t 65 59 brightness, SCAN-C 11:75, ISO% 85.5 86.0 3 25 cohesiveness, m / kg 19 21 suction speed, s 6.5 6.0 suction power, g H 2 O / g mass 10.4 10.8 sheath weight, mean, g 31.9 32.0, standard deviation, g -1.5 -1.0 30

The table shows that the energy consumption was lower when using the invention. Compared to the use of sulphite pulp alone, as in Example 1, the mixing of the ground pulp resulted in a surprisingly low energy consumption. It is further shown from the table that the process according to the invention gave the product better properties throughout. Particularly surprising is the lower dispersion obtained in the diaper weight.

The invention is not limited to the embodiments shown. Thus, it is also possible that, after drying and tearing the pulp, it is mixed with some other dried and torn pulp of another quality, e.g. sulphate pulp or hot milling. Within the scope of the invention, it is also possible to mix the dried and torn pulp with the conventionally flake-dried pulp. Other types of fibers that can be blended in the lance of the dried and then coarse-shredded pulp include, for example, recycled pulp fibers and man-made fibers.

According to the invention, larger units other than straight side bales can also be used. Thus, it is possible to produce larger units by filling the dried and coarse-grained mass into plastic packages of varying shapes and sizes and compressing them to the desired density.

Example 3 In a sulphite mill producing a 2-stage pulp bleached spruce sulphite pulp with a viscosity of 1100 cm -1 and an ISO brightness of 93%, a fiberizing member was installed after the dryer to break up the pulp web. The defibering member comprised a rotating roll equipped with sharp pyramid-shaped spikes. The defibering member is commonly referred to as a spike roll and is normally used to coarsely tear the moist pulp prior to conventional flake drying.

The dry matter content of the pulp at the time of tearing was 93.5%.

30 Tearing gave flakes with a mean width of about 15 mm and a mean length of about 20 mm. The pulp flakes were fed to a plate press and then to a bale press. In the experiment, larger units were prepared in the form of straight-sided bales weighing 180 g of dry mass. 35 The bales were 47 cm high, 91 cm long and 65 cm wide.

3 This gave each bale a density of 650 kg / m. After air conditioning of 2 9,9323 cones, the flake bales were transported to a conversion plant to make diapers. Their dry matter content was then 91.5%. In this factory, a bale containing flakes was opened and torn into small pieces using a simple 5 stick ripper. The size and number of these were the same as those of the flakes obtained before baling at the pulp mill. The pulp flakes were introduced into a disc mill with a transport screw as a shredded pulp. In the experiment, it was found that the pulp bale was easy to tear 10 and the pulp was easy to defiber. It was further found that the disadvantages caused by static electricity were significantly lower than normal. At the test, diapers weighing about 32 g were made. The weight dispersion of the diapers was -1 g and was completely satisfactory. The cohesiveness 15 and absorbency of the pulp were checked before the diapers were made. The result is shown in Table 3 below.

For comparison, a sheet pulp was taken from the mill and stacked in the usual manner and compressed into bales of the same dimensions as mentioned above. The bales weighed 20,190 kg (dry) and had a density of 685 kg / m 2. The dry matter content of the pulp immediately after the web dryer was 93%. After two weeks of conditioning, the dry matter content was 92.0%. The pulp bales were then transported to a conversion plant where they were broken into strips with a guillotine. The strips were 5 cm wide and 80 cm long. The pulp strips were conveyed by a belt conveyor to a hammer mill where they were reduced to flakes with a mean length of about 20 mm and a mean width of about 15 mm. The pulp flakes were introduced into the disc mill with fiber-30 using transport screws. No difficulties were observed in making sheaths from fibrous pulp, except for certain problems caused by static electricity. At the test, diapers weighing about 32 g were made.

The scatter in the diaper weight was -1.

35 The cohesiveness and absorbency of the pulp were checked immediately after defibering, i.e. just before the diapers were made.

______ - TT _____ 10 69323

The results are shown in the following table. All measurements were performed in accordance with SCAN-C 33:80.

Table 3 5 Comparative test Invention total energy consumption, kWh / t 71 62 3 cohesiveness, m / kg 18 20 suction speed, s 6.0 5.5 10 suction power, g i ^ Q / g mass 10.0 10.5

As can be seen from the table, spike-roll tearing of the pulp web has also resulted in lower energy consumption than conventional tearing and defibering. In addition, 15 better end products have been obtained.

Claims (6)

11 69323 A process for the preparation of a starting material suitable for further processing into an absorption product, in which web-dried pulps are used as raw materials, characterized in that the dried pulp, closely connected to a pulp mill web dryer, is broken down into flakes and the resulting flakes are compressed into larger units for easy handling and transport. 3 with a spreading density of 200-800 kg / m 3, preferably 300-700 kg / m 3. Process according to Claim 1, characterized in that at least 70% of the web-dried pulp is decomposed to form particles (flakes) with a mean length / width or diameter of 2 to 70 mm, preferably 3 to 40 mm. Process according to Claims 1 to 2, characterized in that the dry matter content of the web-dried pulp is at least 80%. A method according to claims 1-3, characterized in that the web-dried pulp is cut into sheets which are loosely stacked on top of each other, after which the sheet stack is cut into strips which are broken up into flakes which are then compressed to form larger units. Method according to Claims 1 to 3, characterized in that the dried pulp web immediately after the web dryer is broken up into flakes, which are then compressed to form larger units. Process according to Claims 1 to 5, characterized in that the flakes compressed into larger units are, after intermediate storage, introduced into a conversion plant into fibrous shredded pulp and further into processed absorption products.