JPS59173395A - Production of modified mechanical pulp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing improved groundwood pulp from wood in the form of Kuta mahatata chips.

Jf′f,-! It is known to produce groundwood pulp by bringing logs or chips into contact with a rotating grindstone. The resulting fiber suspension is then treated in a full screen to remove coarse particles, which are then treated in a defibration device, such as a disc refiner, and returned to the fiber suspension. , those that pass are sent to the main screening department.

The rejects obtained from the main screening section are normally returned to the disc refiner, and the passthroughs are optionally purified in a portex cleaner and then (optionally bleached) before being directed to a wet mason or papermaking machine. be done.

O'J Ming a > Kaihe A technical challenge.

Groundwood pulp is commonly used in the production of newsprint and other types of printing paper, and also in the production of soft crepe paper. In the production of papers of these qualities, high demands are placed on a low binding fiber content, ie a partially defibrated wood residue content.

In paper manufacturing, high binding fiber content results in web breakage, imparts a high degree of surface roughness to the paper, and develops printing irregularities. Therefore, a significant challenge in the production of groundwood pulp is to achieve the desired low binding fiber content. The pulp used in the production of paper of said quality has a relatively low freeness, i.e. between 70 and 200 C.
, S, F, are ground. Groundwood pulp is also used in the manufacture of cardboard and paperboard, and here again it is desirable to obtain a pulp with a low binding fiber content. The groundwood pulp used to make paperboard must have a relatively high freeness, ie 250 to 400 C, S, F. However, the disadvantage of milling to high freeness is that the pulp has a relatively high cohesive fiber content and is relatively weak.

In recent years, a thermomechanical valve called a gemothermomechanical valve called C'VM I' and +nHS has been developed. This pulp has an extremely high freeness, 400 to 700 m12 C,S,F, and a low binding F content, making it highly suitable for the production of absorbent products. 50 (l d
It is not possible to produce a practical pulp with higher freeness than C, S, F. Groundwood pulp with such high freeness contains only a small percentage of fibers and consists mainly of bound fibers and debris and cannot be used to make absorbent products.

Solution--Tuesday-Issue O1 The problems mentioned above are solved by the present invention, which relates to an improved method for producing groundwood pulp. In this method, the fiber 1 suspension leaving the grinder passes through a pull screen and is then screened in a main screen section, and the resulting screen waste is treated in a fibrillator and returned to the main screening section. Ru. The method uses 1't of coarsely screened fibers arriving from a 7-column inter in the main screening section. From the turbid liquid a consciously higher than usual amount of 30% or more that does not pass through the screen is removed as a pulp fraction that does not pass through the screen and is treated in a first separation means, in which 4, preferably 8 Bind fibers and debris having a length exceeding 100 mm are removed as a non-passage fraction, defibrated and returned to the main screening section, while the flow from the first separating means is passed through the first separating means in the form of a fractionating means. △) at least 80% of the fibers remaining on the Hauer, Manokunenoto screen with 59 mesh/cm
B) 15 to 60 fibers passing through the Hauer, Manokunenoto screen with 59 meshes/cm;
% of the short fiber fraction, the long fiber fraction is dehydrated and removed from this process for use for a specific purpose, and the short fiber fraction is separated from the filtrate arriving from the main screening section. To mix with minutes! I! R sign and 14 ゛ro.

Benefits - - Benefits With the proposed method, it is possible to use LWC paper (LWC = light 9 coach ink paper) with low energy consumption.
The result is a virtually cohesive fiber-free groundwood pulp of very high opacity with low surface roughness suitable for the production of paper and for blending into other high-quality printing papers. The separated removed long fiber fraction, manufactured with extremely low energy consumption, has a low resin content and high freeness (approximately 200 to 700 dC, S, F, ), high bulk and good properties. It can be suitably mixed into valves intended for use in absorbent products of very high absorption rate and absorption capacity and intended for the manufacture of paperboard or paperboard. By the method according to the invention it is possible to bring the properties of groundwood pulp up to the level of CT MP valves while keeping the energy consumption low.

FIG. 1 is a block diagram of the production of ground wood pulp according to the known technique, and FIG. 2 is a block diagram of the method according to the invention.

According to the known technique shown in FIG. 1, logs or wood knobs are ground in a grinder I.

The fiber suspension leaving the grinder contains knots, splinters and other coarse wood residues and is passed through conduit 2 to a coarse screening section in the form of a pull screen 3 (knotter). The pull screen can consist of a so-called vibrating screen, ie a screen structure with vibrating screen plates provided with holes or slots.

The coarse screened coarse material, typically having a length of about 50 wn or more, is passed through conduit 4 to defibration means 5, such as a disc refiner, and the defibrated material then passes through conduit 6. through which the fiber suspension leaving the grinder is returned, for example to conduit 2. The fiber suspension from which coarse wood residue has been removed is removed from the pull screen through conduit 7;
The core portion 8 sent to the main screening portion 8 is, in its simplest form, a perforated screen plate and two
For example, it may consist of a pressurized screen having a diameter of 1.75 mm. Up to about 20 tonne percent of the fiber suspension entering the main screening section is separated as rejects, and the screen shown in FIG. optionally after passing through the defibration means 5 as shown in Figure 1, it is returned to the circuit through conduit 6. The pass-through obtained in the main screening section is taken off through conduit 10 and 9' : Xff17(] to 200 m!Q C, S, F, freeness and binding fiber content of 0°08 to 1.20%. The flowthrough is optionally cleaned in a portex cleaner and then Sent to wet pussy.

During the production of groundwood pulp according to the present invention (Second Part 1), four thousand knobs of logs or wood are ground in a tarinder 1. The fiber suspension leaving the tarinder is passed through conduit 2 to the sol screen 3 and by the screen 3 (the separated end residue is passed through conduit 4 to a defibration device 5, e.g. a disc refiner). The material conveyed and defibrated therefrom leaves the ζtalinder in the same manner as illustrated in FIG. In the main screening section 8, for example, by increasing the amount of passing flow (increasing the opening of the valve 17),
or by reducing the hole diameter of the screen plate, or by a combination of both, so that between 30 and 80% by weight of the fiber suspension Q) arriving through conduit 7 is separated out as rejects. The amount of throughput is increased. The resulting reject pulp fraction is passed through conduit 9 to a first separation means 11 for separating residual bundle fibers and debris having a length of more than 4 m, preferably more than 8 m11. The first separating means can be, for example, a vibrating screen with a large strip smaller than the vibrating screen 3. The rejects from the first separating means II are returned to the defibrating means 5 through a conduit 12. and from there said fraction is returned to the suspension leaving the grinder, e.g. conduit 2. The pulp fraction that has passed on the other hand is passed through conduit 13 through a screen according to Hauer and Masochnenoto with a diameter of 59 mesos/cm. The long fiber fraction containing at least 80% of mfl(6°) and the long fiber fraction containing at least 80% of mfl(6°) and
Noshi 5. A second filter, which can be, for example, a centrifugal screen or a curved screen, is used to separate the passed-through fraction into a short fiber fraction containing 15 to 60% of the fibers that pass through the screen according to Hauer, Manokunenoto, having a diameter of is sent to the separation means 14 of.

The long fiber fraction is removed through conduit 16, while the short fiber fraction is removed through conduit 15 and left in conduit 10 leaving the main screening section to form a second short fiber fraction. is sent to the throughflow of

In order to produce the effect sought according to the invention, the outgoing material streams 13 and C of processes 1 and 2 must have a weight ratio between long fiber fraction and short fiber fraction of 1=3 to 3:l. must be adjusted to fit the range.

According to a particularly preferred embodiment of the invention, the white water obtained when dewatering the long fiber fraction is returned as dilution water to the first separation means II and, if desired, a separation filter can be installed in the circuit. By putting in the effort, V can achieve 20
[]mg/(L) or less fiber content.

Since a large amount of rejects are removed from the main screening section 8 when the current is passed through the conduit 10, the M fraction has an extremely low binding fiber content and 0.
0 to I), within the range of 0.05%.

The corresponding known groundwood pulp of comparable freeness is 0.
(Has a binding fiber content of 1B to 0.20%.

This oat's cohesive fiber content significantly impairs the usefulness of the pulp in the manufacture of printing paper, contributes to surface roughness in the paper, and renders the paper non-uniformly absorbent in ink. In addition, the short fiber fraction produced by the present invention has a fiber distribution different from that of ordinary groundwood pulp, which means that the paper made from said fraction is more suitable for printing paper than the paper made from ordinary groundwood pulp. achieves the benefit of having a higher tensile index and opacity in It is therefore highly suitable for manufacturing top quality printing papers.

The long fiber fraction according to the invention obtained through conduit 16 has a high freeness (200 to 750 C, S, F).
and 0.3% I) with a low resin content (less than 0.15% DKM after bleaching) than KM, and 80 to 100% of said fractions have 59 mesos/cm. It consists of a t-shirt that remains on the screen. This long fiber fraction has excellent properties for the manufacture of absorbent products, offering high bulk properties, good absorption rates and very good absorption capacity. In the method according to the invention, 15 to 7
5% is recovered as a fraction.

In this way, Chemithermomechanical pulp (C1” M
1)) Instead of producing a ql-product inferior to ! The total energy consumption when producing fraction II is between 300 and 500 kWh per dry pulp, whereas the corresponding value for Gemithermomechanical pulp is approximately 1 (l O(l k W l+) per dry pulp. Because of this, such products are produced using less energy and with higher yields.When producing short fiber fractions, the energy consumption is 130% per
0 to 150 (lkWh, but the corresponding quality OC
The corresponding value for T M P is approximately 2000 kWh per L of dry pulp.

When practicing the present invention, at least 96% of the wood is converted to pulp (92 to 94% for CT"MP)
).

The long fiber fraction produced according to the invention is well suited for blending with other pulps such as sulfide pulps, sulfate pulps and chemi-mechanical pulps.

It is highly suitable for the production of cardboard and paperboard and also for the production of absorbent products. Other fibrous materials such as recovered fibers, beet fibers and synthetic paper may also be mixed with the long fiber fraction.

The method according to the invention can also be applied with good results to the production of pressed groundwood pulp, in which case the energy consumption is still low (approximately 10% lower).

The invention is illustrated in the following examples.

EXAMPLE Groundwood pulp was produced from spruce according to known techniques (see FIG. 1). Crush the spruce with a grinder (l♀),
The fiber suspension at a concentration of 2.1% was passed through conduit 2 to a vibrating screen 3 of the Jenson type having a screen plate perforated with six fin holes in the rectangular diameter, where the coarse wood+4 residue was removed. Approximately 3 of the incoming fiber suspension obtained on the vibrating screen and consisting of coarse debris and bundled fibers
The non-passage portion, which accounts for % by weight, is traced through the transport conduit 4 to a concentration of 5%.
Then, the coarse raw material was sent to disc refiner 5 for defibration into IIIJ fibers. The defibrated unfiltered pulp passes through conduit 6 and conduit 2 and is returned to vibrating screen 3 7
Ta. The pass-through from the vibrating screen 3 has a concentration of 1.3% and is sent through a conduit 7 to a pressurized screen 8, i.e. a screen with a fixed cylindrical screen press 1-, against its cylindrical inner surface. The pulp suspension is delivered under overpressure. The screen was equipped with an internal rotating scraper means and the perforated screen plate of the pressurized screen had a hole diameter of 1.75 vavh. The flow of the fiber suspension to the pressurized screen is such that 20% by weight of the fiber content of the fed fiber suspension is
It was controlled to remain at the top and further follow pulp 17, conduit 9, conduit 4, be further processed in disc refiner 5, and be returned to conduit 2. conduit 9
The pulp concentration was 1.9%. The pass-through from the pressurized screen had a pulp concentration of 1.1% and was removed through conduit IO and further cleaned in a portex cleaner. Here, the sample named 8 was removed for determination of bundled fiber content and fiber composition.

In accordance with the present invention, the groundwood pulp manufacturing method was modified as shown in FIG. Therefore, the grinder 1 is passed through the conduit 2.
The fiber π suspension arriving from and having a concentration of 2.1% is coarsely screened in a vibrating screen 3 with hole diameter 61, and the rejects, which account for 3% by weight of the incoming fiber suspension, are passed through conduit 4. The M'-fibered reject pulp having a pulp concentration of 5% is then sent through conduit 6 and conduit 2 to a disc refiner 5 with a pulp concentration of 5%.・It was returned to me. The pass-through from vibrating screen 3 had a concentration of 1.3% and was sent through conduit 7 to pressurized screen 8.

In this case the screen plate of the pressurized screen has a hole diameter of 1.60 I instead of 1.711 IM in the previous case.
The hole diameter was changed to Im. At the same time, the pulp 17 was further opened and the amount of non-passing pulp was increased to 70% by weight of the fiber content of the incoming fiber suspension. The non-passable pulp fraction that was cracked on the pressurized screen 8 had a freeness of 245 C, S, F, and a binding fiber content of 5't 2.9
5%, 7.9 mesos/cm non-passage 33°1%, 5
It had a fiber composition according to Hauer, Manokunenoto of 41.5% passing 9 mesos/cm, and 25.4% passing 59 mesos/cm. The non-passing pulp is given a pulp consistency of 1.5% and passes through conduit 9,
It was sent to a first fraction 1 means in the form of a vibrating screen 11 equipped with a screen plate 1~ having a hole diameter of 3.01 mm. The vibrating screen 11 contains fibers that do not pass through.
', 'The content was adjusted to 0.8% by weight of the J effluent. The non-passage pulp obtained from the vibrating screen 11 has a Zumerville bound fiber content of 73% and is sent through conduit 12 for further processing in the disc refiner 5 and through conduit 6 and conduit 2. It was returned. The pulp concentration in conduits 6 and 2 was the same as in tests conducted according to known methods. The pass-through pulp from the vibrating screen 11 was given a pulp consistency of 1.2% and was sent through conduit 13 to a second separation means 14 where it was fractionated. This fractionation means consists of a centrifugal screen of the Cowan type, ie a screen with a stationary cylindrical screen plate, against the cylindrical inner surface of which the fiber suspension is launched by means of a rotating device. Unlike vibrating screens, centrifugal screens are constructed to take advantage of the mutual self-growth effect of fibers falling on the screen surface.
and has a larger hole diameter.

The centrifugal screen had a hole diameter of 1.50 am. The pass-through fraction obtained from the screen has a freeness of 1
4 (1 m C, S, F) and a bound fiber content of 0.04% according to Zimmerhill;
．． 1% and 59 mesh/cm Rejected 82% and 59
It had a mesoso, +, /cm passage of 14%.

The pass-through fraction is given a pulp concentration of 0.9% and the flow of the pass-through from the pressurized screen 8 through the conducting layer I5...
・This passing flow has a freeness of 90 smoke C, S,
F, , Bundled fiber content 0. CIt%, and 7゜1) Mesosifu-/cm Rejected fraction 2.3%, 59 Mesosifu-/
cm Rejected 63.7%, and 59 mesos/cm
It had a fiber distribution according to Hauer and Masokunesoto with a passing rate of 34%. Pressurized screen 8 and centrifugal screen 14
The mixed pass-through fiber fraction from was removed through conduit 10 for cleaning in a portex cleaner (not shown). Fibers leaving vibrating screen 11 through conduit 13! , 20% of the suspension was removed in the centrifugal screen 14 as a flow through. A sample designated B here was taken from the short fiber fraction in conduit 10 for measurements of bundle fiber content 9 and fiber distribution. The amount of short fiber fraction calculated on the incoming wood material is 44%, of which 31
．． 2% was in conduit ■5. The non-passage fraction from the centrifugal screen ■4 leaves the vibrating screen 11 for fibers ¥/!
, accounting for 80% of the suspension, giving a pulp concentration of 1.9%, and was removed through conduit 16 as the long fiber fraction. The ratio of short fiber fraction to long fiber fraction was 1:2.2.

A sample, designated C, was removed through conduit 16 for determination of bundle fiber content and fiber composition.

Table ■ below shows the bundled fiber content and fiber distribution of the collected samples. A represents the known groundwood pulp, B and C represent the groundwood pulp according to the invention, of which B represents the short fiber fraction and C represents the long fiber fraction. Typical values for Chemi-Momechanical Pulp D (CTML) are also shown for comparison.

It can be seen from Table 1 that the short fiber fraction produced according to the invention has a very low binding fiber content. The long fiber fraction produced by the present invention has very high freeness and
It has a low bound fiber content and a very high long fiber content.

A portion of the collected sample was 3% by weight per L of dry pulp.
of hydrogen peroxide, washed with water, dehydrated and dried on laboratory sheets and analyzed for extractables content and whiteness. A portion of the laboratory sheet was ground into a fluffed pulp in a disc refiner and the bulk, absorption rate and absorption capacity were measured. The results obtained are shown in Table H below.

Sample E relates to cyphite pulp, which is a chemical pulp.

(Left below) From Table II, it can be seen that the long fiber fraction C produced according to the present invention has exceptionally high values for bulk and absorbent capacity, and has a high yield, which was previously considered the best for producing absorbent products. It is comparable to chemi-thermomechanical pulp, which is a high-temperature pulp. The properties of long fiber fraction are significantly better than sulfide pulp. The long fiber fraction also has a significantly lower resin content than CTMP, and at the same time a significantly greater whiteness.

This high degree of whiteness is surprising because of the low light scattering coefficient of this pulp.

Paper was produced from samples A and B and the technical properties of the paper were evaluated. The results are shown in Table ■ below.

(Left below) The short fiber fraction produced according to the invention thus had a higher tensile index and significantly higher opacity than the M-sized groundwood pulp.

Therefore, when carrying out the method according to the invention, through the groundwood pulp production process, improved pulp for a wide range of applications such as fine pulp for the production of high quality printing paper and coarse pulp for the production of fluff and cardboard is produced. It is possible to produce pulp using less energy than usual.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a method for producing groundwood pulp according to a known technique, and FIG. 2 is a block diagram of a method for producing groundwood pulp according to the present invention. l is the grinder, 3, 8, 11.14 is the screen,
5 is a disc refiner-117 is a Harz. Patent applicant Mo, Onoku, Tom Joe, Aktieporag agent Patent attorney Taku Akaoka, husband ゛1

Claims (1)

[Claims] (11) The fiber suspension leaving the grinder is screened in a main screening section after rough screening, and the portion that does not pass through the screen is processed by a fibrillation means,
And in the production process of the groundwood pulp that is returned to the main screening department, in the main screening department, more than four volumes, i.e., more than 30% No.9
The pulp fraction that did not pass through the screen was removed, and the pulp fraction that did not pass through the screen exceeded 4. Preferably, the bundled fibers and debris having a length of more than 8 lengths are treated in a first separation means to form a non-passage fraction, the non-passage fraction being defibrated and returned to the main screening section, while the non-passage fraction is The pass-through from the first separation means is processed in a second separation means in the form of a fractionation means such that at least 80% of the fibers remain in the screen according to Hauer, Masoknesoto, 59 Metsuyu/Cm.
B) a long fiber fraction containing 59 mesh/cm;
10% short fiber fraction, the long fiber fraction is dehydrated and removed from the process for specific purposes, and the short fiber fraction is separated from the flow-through arriving from the main screening section. An improved method for producing groundwood pulp characterized by mixing. (2) The method according to item 1, wherein the weight ratio of the long fiber fraction to the linear short fiber fraction is 1=3 to 3:1. (3) A method according to claim 1, characterized in that 15 to 75% of the incoming wood material is removed as the long fiber fraction. (4) The method according to item 1, wherein the screening and fibrillation operations are carried out in such a manner that the content of bundled fibers in the short fiber fraction is 0.05% or less.