JPS6354836B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention can be applied to, for example, bagasse (cane dregs), bamboo,
It relates to a method for mechanically pulping non-wood fiber raw materials such as kenaf with a high yield of 75-90%. Many methods have been proposed for high-yield pulping of bagasse. Among them, as shown in JP-A-55-62288, bagasse is pretreated with a small amount of alkaline chemicals and then heated under pressure to improve the yield.
It has a high strength of 75 to 90% and has excellent strength properties, so it is suitable for so-called C, which is refined into pulp by refining.
-The TMP method is said to be suitable for producing pulp, the main raw material for newsprint-grade writing and printing paper. However, when non-wood fibers are refined using a small amount of alkaline chemicals, the resulting pulp tends to be very non-uniform. In other words, the slit width is 0.15 mm from the one that passes through 300 mesh cloth.
Pulp is distributed over a wide range including those that do not pass through the screen. In particular, fibers that do not pass through a slit width of 0.15 mm are generally called binding fibers, which can cause paper breakage during papermaking, and if they are included in the final paper product, they can cause problems such as peeling off from the paper surface during printing. Must not be included. To this end, it is common practice to increase the number of stages of repeated processing in the refiner or to make the grinding plates of the refiner narrower, but this will abnormally increase the proportion of fine fibers and reduce the water content of the pulp. A problem arises in that paper manufacturing becomes difficult. Generally, the freeness of mechanical pulp, which is the main raw material for newspaper, is 80~
It is said that 150ml CSF (Canadian Standard Freeness) is desirable. By the way, the present inventors conducted an experiment in which non-wood fibers such as bagasse, bamboo, and kenaf were mechanically pulped using a refiner, and as a result, the following findings were obtained.
In other words, non-wood fiber raw materials are distributed over a wide range, from components that are easily separated into single fibers when treated with a refiner (referred to as soft components) to components that are difficult to separate into single fibers (referred to as hard components). There is. When this soft component is pretreated and mechanically treated in the presence of an alkaline chemical solution, it not only separates into the above-mentioned single fibers, but also damages the fibers and becomes fine fiber pieces, which abnormally reduces the freeness of the pulp. . On the other hand, hard components are vertical and rigid, and if they are forcibly treated with a refiner, the fibers will break and crumble will occur, resulting in a very weak pulp strength. Therefore, the present inventors focused on the fact that non-wood fiber raw materials have different characteristics when compared to the mechanical processing by such a refiner, and as a result of their studies, they found that mechanical pulping of non-wood fiber raw materials could solve the conventional problems. He came to invent a law. That is, the non-wood fiber raw material is first pretreated in the presence of an alkaline chemical solution, and then mechanically treated with a disc ironer under pressure and heat to achieve freeness.
Obtain an intermediate pulp of 250 to 600 ml CSF, and then divide this intermediate pulp into a fine pulp that does not contain binding fibers and a coarse pulp that contains binding fibers, and the ratio of the fine pulp to the coarse pulp is 70:30 to 50:50. Then, the coarse pulp is further subjected to a second pretreatment in the presence of an alkaline chemical solution, and the ratio of the alkaline chemical solution in the first pretreatment and the second pretreatment is 6 on the basis of Na ₂ O. : Adjusted in the range of 1 to 1:1, and then the coarse pulp subjected to this secondary pretreatment was mechanically treated with a disk-cliff eyeliner.
A method of mechanically pulping a non-wood fiber raw material, which is characterized by mixing it with the separated thin pulp described above. According to this method, a finished pulp with high freeness (good aqueous property), low binding fibers, and high strength can be obtained. is obtained, thus improving the paper-making properties when making paper from pulp and improving the printability of paper products. Furthermore, since the fiber raw material is effectively refined, the required refining power is reduced. In addition, the proportion of alkaline chemical solution
Since the ratio is adjusted to a range of 6:1 to 1:1 based on Na ₂ O, it is possible to improve the effect of chemical pretreatment on coarse pulp and prevent a decrease in the strength of fine pulp. An embodiment of the present invention will be described below with reference to FIG. First, non-wood fiber raw materials such as bagasse, bamboo, and kenaf are heated and maintained in the presence of an alkaline chemical solution (primary pretreatment). The alkaline chemicals mentioned above include alkaline earth metal hydroxides (Ca(OH) ₂ ), alkali metal hydroxides (NaOH, etc.), carbonates (Na ₂ CO ₃ ), and sulfites (Na ₂ SO ₃ ). etc. may be used alone or in combination. In particular, when a mixture of NaOH and Na ₂ SO ₃ is used, a pulp with high strength and good whiteness can be obtained. In this case _Na2O and _SO2
and the weight ratio is in the range of 4:1 to 1:1 and
Na ₂ O is 1-5% per bone dry weight of non-wood fiber raw material
It is desirable that it be within the range of . Further, it is desirable that the heating and holding is performed under the same steam pressure as the next refining step. Next, the non-wood fiber raw material that has undergone the first pretreatment is mechanically treated with a discreet eyeliner under pressure and heat to achieve a freeness of 250%.
Obtain an intermediate pulp of ~600 ml CSF (preferably 300-500 ml CSF). The above pressurization and heating are performed using steam with a pressure higher than atmospheric pressure, and the pressure range is
The desired temperature range is 0.2 to 3 Kg/cm ² (gauge pressure) and the desired temperature range is 105 to 140°C. Note that when the freeness of the intermediate pulp becomes less than 250 ml CSF, the proportion of fine fibers that are excessively refined and pass through the 300 mesh increases, and when the freeness exceeds 600 ml, the proportion of bound fibers increases. Next, the intermediate pulp is separated into a thin pipe that does not substantially contain bound fibers and a coarse pulp that contains a large amount of bound fibers. The above separation is carried out in one or two stages using a rotary screen or the like in an aqueous solution having a pulp concentration of 1 to 2%. Note that the ratio of fine pulp to coarse pulp is preferably within the range of 70:30 to 50:50. If the ratio is larger than this, there is a risk that the fine pulp may contain more than the permissible amount of cohesive fibers (usually said to be less than 1%), and if the ratio is smaller than this, the coarse pulp may not require further refining. It will contain a lot of good fiber. Next, only the coarse pulp is heated and held again in the presence of an alkaline chemical solution (secondary pretreatment). In this case, it is preferable to carry out the reaction under atmospheric pressure of 50 to 100°C, but it may also be carried out under pressure of 100°C or higher. In some cases, coarse pulp may be returned to the primary pretreatment step. Processing time is usually 2 to 60 minutes. In addition, the alkaline chemical solution used in the second pretreatment step is the same as the alkaline chemical solution used in the first pretreatment step,
In addition, the total amount of alkaline chemicals used in the primary pretreatment and secondary pretreatment should be such that the amount of Na ₂ O is in the range of 1.5 to 5% based on the original non-wood fiber. is desirable. If the amount of Na ₂ O is small, the hard components will be powdered, the pulp strength will be insufficient, and the refining power will increase. In addition, if the amount of Na ₂ O is too large, the soft components may be excessively refined, the elution by alkali will increase, the yield will decrease, and the whiteness and opacity of the pulp will decrease. Note that the ratio of the alkaline chemicals used in the primary pretreatment and the secondary pretreatment is preferably in the range of 6:1 to 1:1. If the ratio is larger than this, the effect of chemical pretreatment on coarse pulp will be reduced, and if the ratio is smaller than this ratio, the strength of fine pulp will be significantly lowered, which is disadvantageous. Next, the coarse pulp that has been subjected to the secondary pretreatment is again passed through an atmospheric pressure type disk clarifier.
Perform one-stage or two-stage processing. Note that refining is desirably carried out at a pulp concentration of 10 to 30%. Further, the pulp after refining may be returned to the above-mentioned separation step as the case may be. Then, the thin pulp obtained in the separation process,
The pulp obtained in the above-mentioned refining process is mixed, and if necessary, dust removal and bleaching are performed to obtain raw material pulp for newspapers and the like. According to the above method, a finished pulp with high freeness (good aqueous property), low binding fibers, and high strength can be obtained, which improves the formability when making paper from pulp and improves the printability of paper products. gets better. Furthermore, since the fiber raw material is effectively refined, the required refining power is reduced. Next, a specific example will be explained. Γ Specific example 1 Alkaline sodium sulfite is added to depissed picabagasse produced in Indopasia (from which the pis content has been removed from sugarcane residue), and 3.4% as Na ₂ O and 1.2% as SC ₂ are added based on the absolute dry weight of depissed bagasse.
After heat treatment with steam at 120° C. for 4 minutes, one-stage refining treatment was carried out using a pressurized disk stiffener with a disk diameter of 610 mm and maintained at 120° C. The freeness of the pulp after refining was 350 ml CSF. Next, this was diluted with water to make a pulp liquid with a concentration of 1.1%, and was supplied to a rotary screen with 2.2 mm holes to separate fine pulp that passed through the screen and coarse pulp that did not. The ratio of fine pulp to coarse pulp is
It was 55:45. Pretreatment was carried out by adding alkaline sodium sulfite to the coarse pulp and adding 0.7% as Na ₂ O and 0.3% as SO ₂ based on the original depissed bagasse bone dry weight, and holding the pulp at a pulp concentration of 5% and a temperature of 80°C for 30 minutes. After that, the pulp was deliquified until the pulp concentration reached 20%, and then fed to an atmospheric pressure type disc refining machine with a disc diameter of 610 mm to perform a refining process. The total yield of this refined pulp and fine pulp was 83% of the original depissed bagasse. The pulping test results are shown in Table-1. Comparing the pulp produced by the method of the present invention (Sample No. 5) and the pulp produced by the conventional method (Sample No. 6), the pulp produced by the method of the present invention has high freeness, low binding fiber content, and excellent strength properties. Also,
The method of the present invention requires less refining power. The pulp produced by the conventional method (sample No. 6) was pretreated with 4.1% Na ₂ O and 1.5% SO ₂ and then subjected to pressure refining, followed by atmospheric pressure refining without separation. It is something that has become familiar. Γ Specific example 2 Alkaline sodium sulfite was added to depissed bagasse produced in Thailand with 2.6% Na ₂ O and 0.8% SO ₂ based on the bone dry weight of the depissed bagasse, and heat treated with steam at 125°C for 5 minutes. 125 with a pressurized disk cliff eyeliner with a disk diameter of 610 mm.
A one-stage refining process was performed while maintaining the temperature at °C. The freeness of the obtained pulp is 470ml
The bound fiber content in CSF was 10.2%. Refining power per ton of original bagasse
It was 900KWH. Next, dilute this refined pulp with water to a pulp concentration of 1%.
Supplied to a rotary screen with 1.8mm eye holes,
The pulp was separated into a thin pulp that passed through the screen and a pulp that did not. The ratio of fine pulp to coarse pulp was 60:40. Next, alkaline sodium sulfite was added to this coarse pulp, based on the bone-dry weight of the original depissed bagasse, 1% as Na ₂ O and 0.3% as SO ₂ was added, and the mixture was fed into a twin-screw mixer and heated with steam to form the pulp. The mixture was stirred for 5 minutes at a concentration of 15% and a temperature of 90°C, and then fed to an atmospheric pressure disc refining machine with a disc diameter of 610 mm for refining. The total yield of this refined pulp and the thin pulp was 86% based on the original depissed bagasse. For comparison, the coarse pulp was subjected to refining without the alkaline addition pretreatment step. Table 2 shows these pulping results. The pulp (Sample No. 10) obtained by re-refining coarse pulp by the method of the present invention after pre-treatment has fewer bundled fibers and high strength, but the pulp obtained by re-refining coarse pulp without pre-treatment as shown in the comparative example (Sample No. .11) has the disadvantage that the strength of the pulp, especially the tensile strength indicated by the breaking length, is extremely low.

【table】

[Table] By the way, in Specific Example 1, the plate spacing of the first stage pressurized disc lift eyeer was adjusted,
By changing the refining power, intermediate pulps with various freenesses were obtained. The inlet concentration of the rotary screen was then adjusted to separate this intermediate pulp into fine and coarse pulps, maintaining approximately a 55:45 ratio. The relationship between the freeness of the intermediate pulp, the freeness of the fine pulp, and the content of bound fibers in the fine pulp was determined. The results are shown in the graph of FIG. If the reflining is performed excessively and the freeness of the intermediate pulp is reduced to below 250ml CSF, the freeness of the thin pulp will be abnormally reduced, while if the reflining is insufficient, the freeness of the intermediate pulp will be reduced to 600ml.
When the content was higher than CSF, a problem occurred in which the content of bound fibers in the thin pulp increased abnormally. Further, in Specific Example 2, in the intermediate pulp separation step, the ratio of fine pulp to coarse pulp to be separated was changed by changing the hole diameter of the rotary screen.
The results of measuring the freeness of the coarse pulp and the content of bound fibers in the fine pulp are shown in the graph of FIG. If the ratio of fine pulp to coarse pulp is greater than 70:30, the proportion of bound fibers in the fine pulp will abnormally increase, which is a problem. On the other hand, it was determined that when the ratio is smaller than 50:50, the freeness of the coarse pulp decreases and the proportion of good fibers that do not require further refining increases in the coarse pulp.

[Brief explanation of drawings]

Fig. 1 is a process diagram of an embodiment of the present invention, Fig. 2 is a graph showing fine pulp freeness relative to intermediate pulp freeness and binding fiber content in the fine pulp, and Fig. 3 is a graph showing the ratio of fine pulp to coarse pulp. 1 is a graph showing the freeness of coarse pulp and the bound fiber content in fine pulp.

Claims (1)

[Scope of Claims] 1. A non-wood fiber raw material is first pretreated in the presence of an alkaline chemical solution, and then mechanically treated with a Discliff Eyener under pressure and heat to achieve a freeness of 250%.
Obtain ~600ml CSF of intermediate pulp, and then divide this intermediate pulp into a fine pulp that does not contain binding fibers and a coarse pulp that contains binding fibers, and the ratio of fine pulp to coarse pulp is 70:30 to 50:50. Next, the coarse pulp is further subjected to a second pretreatment in the presence of an alkaline chemical solution, and the ratio of the alkaline chemical solution in the first pretreatment and the _second pretreatment is 6: After adjusting the ratio in the range of 1 to 1:1, and then mechanically treating this secondary pretreated coarse pulp with a disk stiffener,
A method for mechanically pulping a non-wood fiber raw material, which method comprises mixing the above-mentioned separated fine pulp. 2 A mixture of NaOH and Na ₂ SO ₃ is used as the alkaline chemical solution, and the weight ratio of Na ₂ O and SO ₂ is in the range of 4:1 to 1:1, and Na ₂ O is less than the absolute dry weight of the non-wood fiber raw material. A method for mechanically pulping a non-wood fiber raw material according to claim 1, characterized in that the pulping amount is in the range of 1 to 5%. 3. A method for mechanical pulping of non-wood fiber raw materials according to claim 1, characterized in that the coarse pulp is returned to the first pretreatment step. 4. The method for mechanically pulping a non-wood fiber raw material according to claim 1, characterized in that after the coarse pulp is refined, it is returned to the separation step.