JPS6241389A - Mechanical pulping of fibrous material - 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 process for mechanical pulping of fibrous raw materials such as wood chips.

BACKGROUND OF THE INVENTION Today, writing and printing papers such as medium-quality and high-quality papers are manufactured using BKP (Kraft Bleached Chemical Pulp), a hardwood material, as the main raw material. By the way, recently, the use of mechanical pulp as a substitute or a partial substitute for BKP has been attracting attention for the following reasons.

■ Mechanical pulping method has a high pulping yield and allows effective use of cellulose resources.

■ Unlike the chemical pulping process, the mechanical pulping process does not require expensive chemical recovery equipment, resulting in lower equipment costs and lower pulp production costs. However, pulp, which is the main raw material for writing and printing paper such as medium-quality and high-quality paper, is required to have appropriate pulp strength, high whiteness, and low binding fiber content.

Conventionally, as a method to meet the above requirements, hardwood chips are immersed in a NaOH solution at 50'C or less for a certain period of time and then defibrated and pulped using a fast disc refiner, generally referred to as the cold soda method. ) It is known to bleach this with hydrogen peroxide etc. to obtain white pulp, and also to bleach hardwood chips with Na25O3 or NaH803 to obtain white pulp.
It is also known that after pretreatment at a high temperature of 0 to 180° C., the fibers are defibrated and pulped using a disc refiner (generally referred to as the SCMP method), and then bleached with hydrogen peroxide.

Problems to be Solved by the InventionAccording to the method of the above-mentioned IY1, the pulp has a high bundling and is suitable for blending into lower paper such as newsprint, but it requires special bundling when blending into intermediate and high grade papers. There is a problem that it is not suitable unless a device is added to sufficiently remove the fibers. In addition, according to the author's method, the pulp contains less 41i fibers than the cold soda method, but in order to obtain the necessary pulp strength, a large amount of Na2SO3 or Na1-ISO3 is required, so chemical recovery is required. Without it, drug costs would be high.

Therefore, it becomes necessary to install a chemical recovery device, which raises the problem of increased equipment costs.

Therefore, an object of the present invention is to provide a method for mechanical pulping of fibrous raw materials that can solve the above problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the method of mechanically pulping 1tfL fiber raw material of the present invention pre-treats the 41 fiber raw material using an alkaline chemical, and then mechanically pulps it using a disc refiner. In the method of processing and pulping, NaO is added to the fiber raw material.
An alkaline solution containing H as the main component is infiltrated at a temperature below so''c and an alkali consumption rate of 1 to 7%, and then 0% of sodium &Qvi or sodium bisulfite is added to this.
After adding 2 to 2%, the hydrogen peroxide was heated under steam pressure of 0.3 to 2 kg/cmG for 0.3 to 5 minutes, and then pulped with a disc refiner under steam pressure. This is a bleaching method.

EXAMPLE Hereinafter, an example of the present invention will be described based on the flow sheet diagram of FIG. The raw materials used include lignocellulosic substances, including broad-leaved trees such as poplar, birch, and eucalyptus, but also coniferous trees and bagasse (cane dregs).
It is the first non-wood fiber raw material for hats. Na wood chips
Penetration of alkali into wood chips can be prevented by immersing them in a solution containing OH as the main component for a certain period of time, or by immersing them in an alkaline solution for a short period of time, then draining the chips and holding them with excess liquid removed. prompt. The processing temperature at this time is the outside temperature or some
It is preferable to carry out the process in a heated state, usually at 30-50°C.
It is necessary to keep the temperature at most 80"C or lower. If the processing temperature is high, the whiteness of unbleached parbuta will decrease and the bleaching cost 1- will increase, making it uneconomical.

The concentration of #solution used and the treatment time are determined depending on the desired alkali consumption rate. The alkali consumption rate is 1-7% (Na2
0 (based on bone dry weight of feedstock), preferably 1%
If it is less than 7%, the alkali will have no effect on improving pulp strength, and if it is more than 7%, the whiteness of unbleached pulp will drop abnormally, and it will not be possible to bleach it to the whiteness required for the main raw material of intermediate and high-grade printing paper. . Note that in order to improve the penetration of the alkali, the wood chips may be roughly crushed or deaerated by steaming before penetration. As the alkaline solution, NaOH alone or NaOH as the main component such as Na2CO3 or Na2S can be used.
O3 may be used in combination depending on the case.

Next, the raw material after the alkali WI permeation is fed into a steam pressurized container using a screw feeder, rotary feeder, etc., and the raw material is heated here before refining. At this time, add 0.2 to 2% of Na2SOx or Nat-1sO3 (
802 (per bone dry material weight) is added. Steam has a saturated vapor pressure of 0.3-2 k! +/cII, and the raw material holding time here is a short time necessary for heating, preferably 0.2 to 5 minutes. Na2SO3 or Na
H8O3 is highly effective in preventing the whiteness of the raw material from decreasing during this heating and the subsequent refining process. However, 0.2%
Addition of a smaller amount is less effective in preventing this decrease in whiteness. Also, if the amount is more than 2%, the bleaching effect with hydrogen peroxide in the subsequent step will be reduced.

Next, the steam-heated raw material is refined using a disc refiner under steam pressure. This steam pressurization is preferably performed at a saturated steam pressure of 0.3 to 2 kO/calG. Lower than 0.3 ka/cIIG increases the bound Ran content after refining, while 2
When the weight is higher than kg/7, the whiteness of the fine pulp decreases to a greater degree. In addition, in order to satisfy the characteristics such as pulp strength required as a raw material for papermaking, pressure sofaning may be performed in two or three stages, or the pressure refining and atmospheric pressure refining may be performed in one or two stages. .

However, when performing it in combination with atmospheric pressure refining, it is necessary to apply more than 30% of the total refining power to the previous stage pressurized refining. If it is less than 30%, the effect of reducing the binding fiber content is small. Further, these refining raw materials may be treated with a screen or a cleaner in a conventional manner to further reduce the binding fiber content.

Next, the raw material after the refining and viscosity separation is bleached with water peroxide and a bleaching agent to obtain bleached pulp for blending with intermediate and high-grade printing paper. The bleaching conditions for H202 are the usual method, namely, concentration 10-20%, temperature 50-90°C, time 60-200°C.
It is carried out in an alkaline atmosphere of P1]9 to 12 minutes. To obtain bleached pulp with a brightness of 70-80%, H2
It is usually necessary to add 3 to 4% of 02 to the pulp.

Next, a specific example will be explained.

Specific example 1 Brazilian eucalyptus chips were treated with Na under the conditions shown in Table 1.
The permeation-treated raw material containing 60% water content, which was immersed in an OH solution for a certain period of time and then drained with a filter cloth, is fed at a rate of 2 kg/IMin per minute on an absolute dry basis using a screw feeder with an inlet screw diameter of 1501111. Inner diameter 60
0 mm, length 4,000 ni, and at the exit of the screw feeder, add Na2SO3 solution with a concentration of 10 (1/ρ) at a rate of 1.5 Ω/I11 as 802. (1.5% as 802 based on the dry standard weight), while maintaining the inside of the steaming tube with saturated steam of 0.8 kq/cnG, the raw material is rotated from the inlet to the outlet by the rotation of the screw shaft installed in the tube. Adjusted to move in 1.5 minutes, the heated raw material is heated to 0.8 kc+ in a double disc refiner with a disc diameter of 600 ln that rotates in opposite directions.
/cdG under pressure and was continuously discharged through a blow pulp installed at the outlet of the refiner. At this time, the refining concentration was adjusted to about 25% by adding water from the refiner side. Next obtained 1
Next, the pressurized refining raw material was processed in an atmospheric double disc refiner with a disc diameter of 600 mm, and the refining pulp with a freeness of around 20 OnΩ C3F (Canadian standard freeness) was milled. After washing this sofaning-treated pulp with water, 40 (] zumbling on an absolute dry basis, it was disintegrated in a 2 g JIS standard disintegrator at 80 ° C. for 10 minutes,
A part of the material was made into a pulp sheet using the JLS method, and the physical properties of the pulp were tested. The disintegrated raw material 25 () is mixed with a mesh size of 0.
151111 laboratory flat screen to determine the bound fiber content. In addition, the water-washed pulp after the above secondary refining was bench bleached with hydrogen peroxide (1 sample 20 (180 samples each) was placed in a plastic bag, and
%, NaO+-42.2%, and 7% sodium silicate were added and mixed, and kept in a constant temperature bath at 80°C for 120 minutes at a pulp concentration of 10%), and the whiteness of the obtained bleached pulp was measured. . These results are shown in Table 1 and FIG. 2. From these results, it is clear that according to the method of the present invention, pulp that can be blended into intermediate and high-grade writing and printing papers can be obtained.

iJ3, if the alkali consumption in the alkali penetration step is low, the pulp strength will decrease and the refining power will increase, while if the alkali consumption is high, the whiteness of unbleached and bleached products tends to decrease.

In order to formulate intermediate and advanced writing and printing paper, the alkali consumption rate should be 1 to 7% as Na2O based on the absolute dry weight of the raw material.
It is preferably in the range of 2 to 5%.

Furthermore, the treatment temperature in the alkali infiltration step greatly affects the whiteness of unbleached pulp. White color 1 when processing temperature is low
Although the value increases, the alkaline loss 11 tends to decrease and the pulp strength tends to decrease.To counter this, it is necessary to increase the alkali concentration and lengthen the treatment time. On the other hand, if the alkali penetration is carried out at a high temperature, the alkali will be consumed quickly and the treatment will be short-term, making the equipment smaller and cheaper. Preferably, the temperature is 30-50°C.

Specific example 2 Using Brazilian eucalyptus, test No. A of specific example 1
A pulping test was conducted under the same conditions as in Example 5.

However, Na28 added at the screw feeder outlet
The whiteness of unbleached pulp and bleached pulp was measured by varying the concentration of 03 and the addition rate of 802. The results are shown in FIG.

It is clear from this that the method of the present invention with the addition of sulfite in the steaming step improves the whiteness of unbleached and bleached pulps. However, increasing the addition of sulfite reduces the degree of whiteness improvement of unbleached pulp.
In addition, since the bleaching property tends to decrease, the addition rate to the bone dry raw material as 802 is 0.2 to 2%, preferably 0.
．． It is preferably within the range of 5 to 1.0%.

Specific example 3 Using Brazilian eucalyptus, test No. A of specific example 1
A pulping test was conducted under the same conditions as in Example 5.

However, the steam heating time in the steaming tube was changed, and the unbleached whiteness and freeness were 2001ρC3.
The binding fiber content in F was varied. The results are shown in FIG. If it is longer than 5 minutes, the unbleached whiteness will decrease, and if it is less than 0.3 minutes, the uniform heating of the raw material will be reduced.
f? - Lagoon becomes difficult and binding fiber content increases. Desirable steaming times range from 0.3 to 5 minutes, more preferably from 0.5 to 3 minutes.

Specific example 4 Test No. A5 of specific example 1 using Brazilian eucalyptus
A pulping test was conducted under the same conditions.

However, the pressure in the pressurized refining step was varied and the unbleached whiteness and the bound fiber content at a freeness of 200 mJ2C8F were measured. The results are shown in FIG.

From this, according to the method of the present invention which performs pressure refining, the content of bundled fibers can be reduced. however,
If the pressure is increased, the whiteness of unbleached pulp decreases, so the water vapor pressure is in the range of 0.3 to 2 k (1/cd G), preferably 0.6 to 1.5 k (1/cij).

Effects of the Invention According to the above-mentioned method for mechanically pulping a fibrous raw material of the present invention, the following effects are achieved.

■ The pulp strength is such that it can be blended into intermediate and high grade papers.

■ Whiteness increases after bleaching with H2O2.

■ It becomes a uniform pulp with low binding fiber content.

■ High pulp yield compared to kraft methods.

■ Since fewer chemicals are used, there is no need for chemical recovery equipment, so the process is simple and pulp can be manufactured at low cost.

[Brief explanation of drawings]

Fig. 1 is a flowchart of the method of the present invention, and Fig. 2 shows the relationship between alkali consumption, fracture length, and treatment during alkalization.
! A graph showing the relationship between alkali consumption and whiteness of unbleached pulp using degree m as a parameter. Figure 3 shows the relationship between the brightness of unbleached pulp and the brightness of bleached pulp and the addition of M salt in the steaming process. Figure 4 is a graph showing the relationship between steaming time, bundle II content and whiteness of unbleached pulp, and Figure 5 is a graph showing the relationship between steaming time, bundle II content and whiteness of unbleached pulp. It is a graph diagram showing the relationship between bleached pulp whiteness. Agent Morimoto Nishi Hiroki Figure 2 Al〃sujI4 cost amount (NazOYLr／＞length II9'dlr-tif-t
%n Figure 3 AML, #Salt lacquer weight (Sθ2 and 7 pair thread ρ? b singing 10 weight%) Figure 4 S hand - min 7'' B hand rj1 minute) Figure 5

Claims (1)

[Claims] 1. In the method of pre-treating the fibrous raw material with an alkaline chemical and then mechanically treating it with a disc refiner to pulp, the fibrous raw material is treated with an alkaline solution containing NaOH as the main component at a temperature of 80°C or less. Alkali consumption rate is 1
After infiltrating under the conditions of ~7%, then adding 0.2~2% of sodium sulfite or sodium bisulfite,
．． 0.3-5 under steam pressure of 3-2 kg/cm^1G
A method for mechanically pulping a fibrous raw material, which is characterized by holding and heating for a minute, further pulping it in a disc refiner under steam pressure, and then bleaching with hydrogen peroxide.