JP6889595B2 - Pulp production method that facilitates the nano-miniaturization of pulp by the defibration method using high-pressure water flow - Google Patents

Description

The present invention relates to a method for producing raw material pulp that enables nano-miniaturization more easily in a pulp defibration method using a high-pressure water stream.

Cellulose, which is a type of fibrous polysaccharide, is represented by plants such as woody plants such as hardwoods and conifers, herbaceous plants such as bamboo and reeds, some animals represented by sea squirts, and acetic acid bacteria. It is known that it is produced by ascidians. Those having a structure in which these celluloses are aggregated in a fibrous form are called cellulose fibers, and those having a fiber width of 100 nm or less and an aspect ratio of 100 or more are generally called cellulose nanofibers (nanocellulose). Nanocellulose has excellent properties such as light weight, high strength, and low coefficient of thermal expansion, and efforts for its utilization are being actively carried out.

Various methods have been proposed for the production of nanocellulose, including chemical methods such as acid hydrolysis and TEMPO-catalyzed oxidation, and physical methods such as the grinder method, high-pressure homogenizer method, and underwater opposed collision method (ACC method). It is roughly divided into two types of methods. In either method, in order for nanocellulose to spread to the market in the future, it is necessary to improve the manufacturing efficiency and reduce the selling price by reducing the manufacturing cost.

In order to reduce the production cost of nanocellulose, there are a method of increasing the production efficiency of the nano-miniaturization method itself and a method of reviewing the raw materials used for the nano-miniaturization method.

Patent Document 1 has an object of disclosing an expandable and energy-efficient method for producing cellulose nanofibers, and (a) for chemically depolymerizing cell walls and interfiber bonds of cellulose fibers. Depolymerization with a relatively high charge of ozone; or (b) cellulase enzyme; under conditions that promote the formation of free radicals is used. Depolymerization can be estimated by the change in pulp viscosity. After or at the same time as the depolymerization treatment, the treated fibers are mechanically ground. The milling is carried out in one of several mechanical milling devices and the amount of energy savings depends on the type of milling system and the processing conditions. Grinding has disclosed methods of forming cellulose nanofibers that are carried out down to any of several end point measurements such as fiber length,% fine or slurry viscosity.

Patent Document 2 is a fibrillated blend of cellulose pulp having a degree of polymerization of 200 to 1000 and lyocell as measured by ASTM test 1975-96, wherein at least a part of the lyocell fiber has a length of 3 to 12 mm. Disclosure of fibrillated pulp.

Currently, wood-derived pulp (wood pulp) produced by the kraft cooking method, which is widely distributed in general and has an established low-cost production method, is used as a raw material for the production of nanocellulose. Kraft cooking method high temperature wood chips as a raw material with a mixture of NaOH and Na ₂ S, called white liquor (140 to 180 ° C.), obtained by treating for several hours at elevated pressure. However, this production method is a production method for more efficiently producing paper, which is the original purpose, by promoting delignin, and cannot be said to be a raw material suitable for all nano-miniaturization methods.

As a result of the research so far, the present inventors have conducted the pulp used as a raw material in the nano-miniaturization of alkaline cooked bamboo unbleached pulp by the underwater countercollision (ACC) method, which is one of the defibration methods using high-pressure water flow. It has been found that the higher the value of the copper value, which is an index of the amount of residual lignin, the easier it is for nano-miniaturization (Non-Patent Document 1).

In the ACC method, as disclosed in Patent Document 3, natural cellulose fibers suspended in water are introduced into two nozzles (FIGS. 1: 108a, 108b) facing each other in a chamber (FIG. 1: 107). , It is a method of injecting and colliding from these nozzles toward one point (Fig. 1). According to this method, suspended water of natural microcrystalline cellulose fibers (for example, funacell) is made to collide with each other, and the surface thereof is nanofibrillated and peeled off to improve the affinity with water as a carrier. It is possible to reach a state close to dissolution. The device shown in FIG. 1 is of a liquid circulation type, with a tank (FIG. 1: 109), a plunger (FIG. 1: 110), two opposing nozzles (FIGS. 1: 108a, 108b), and heat as needed. A exchanger (FIG. 1: 111) is provided, and fine particles dispersed in water are introduced into two nozzles and injected from the nozzles (FIGS. 1: 108a and 108b) facing each other under high pressure to cause a facing collision in water. In this method, only water is used in addition to the natural cellulose fibers, and nanominiaturization is performed by rupturing only the interaction between the fibers. Therefore, there is no structural change in the cellulose molecules and the degree of polymerization decreases due to the rupture. It is possible to obtain cellulose nanofibers in a minimized state.

The above-mentioned craft cooking method is a cooking method having good delignin property in order to improve whiteness (an index indicating the whiteness of paper), which is one of the important qualities of paper. Therefore, even unbleached pulp has a low copper value, and it cannot be said that it is a raw material that is easily nano-sized in the nano-miniaturization method in the defibration method using a high-pressure water stream.

On the other hand, the alkaline steaming that the present inventors have conducted in the research so far is a steaming method that was used before the invention of the craft steaming method, and is a steaming method in which a mixed solution of raw material chips and NaOH is treated at high temperature and high pressure. It is a solution. However, now that the kraft cooking method has become mainstream, the delignin property is worse than that of kraft cooking, so it is rarely used for industrial production.

Special Table 2015-52169A Special Table 2012-526923 JP-A-2005-270891

2015 Ministry of the Environment Performance Evaluation Business Consignment Business for Cellulose Nanofiber Utilization Research Results Report "Establishment of Low Energy Production Process for Multifunctional Bamboo Nanocellulose"

The present inventors use pulp having a high copper value as a raw material as a condition for making pulp nano-miniaturized by the underwater counter-collision (ACC) method, which is one of the defibration methods using a high-pressure water flow. As a method for producing the pulp, an alkaline cooking method in which cooking proceeds gently was adopted, and relatively mild conditions (alkali addition rate: 15%, 140 ° C.) were found. However, since the cooking is carried out under mild conditions, a large amount of knot lees with insufficient cooking is generated, which causes a problem that it is difficult to actually produce the knots in an industrial manner.

In view of the above problems in the prior art, the present invention enables actual operation by optimizing the cooking temperature and cooking time, and alkaline steaming facilitates the nano-miniaturization of pulp by the defibration method using a high-pressure water stream. It is an object of the present invention to provide the cooking conditions in the solution method.

The present inventors have clarified that in the nano-miniaturization of bamboo pulp by the ACC method, which is one of the defibration methods using a high-pressure water stream, the higher the copper value of the raw material pulp, the easier the nano-miniaturization. However, when bamboo chips were defibrated under these conditions, a large amount of undissolved knot pulp was generated, and it was also found that the conditions were harsh for actual operation (ideally, the knot rate was 5% or less). did. The present inventors have further investigated this point, and have satisfied the knot ratio of 5% or less, which enables actual operation, and an alkaline cooking method for bamboo, which facilitates the nano-miniaturization of pulp by the defibration method using a high-pressure water stream. We found the cooking conditions in.
In addition, the present inventors have found that nano-miniaturization of pulp by a defibration method using a high-pressure water stream proceeds more easily than wood by using bamboo as a raw material.

In the nano-micronization of pulp by the defibration method using high-pressure water flow, it is necessary to cleave the bonds between nanocellulose (mainly hydrogen bonds and van der Waals forces). The cellulose molecules constituting nanocellulose have a hydroxyl group in the side chain, and the nanocellulose are strongly bonded to each other mainly by hydrogen bonds formed by the hydroxyl groups. Pulp, which is a raw material, is an aggregate of nanocellulose, and the wood, bamboo, etc., which are the basis of the pulp, contain a large amount of components other than cellulose, such as lignin and hemicellulose, in addition to nanocellulose. Pulp prepared for the production of general paper removes as much as possible components other than cellulose that originally existed between nanocellulose, so that many hydrogen bonds are formed between nanocellulose. It is thought that this makes nano-miniaturization difficult.
According to the present invention, by pulping in a state where the value of copper value, which is an index of the amount of residual lignin, is high, the lignin remaining (spotted) in the pulp during nanominiaturization forms a bond between nanocellulose. It becomes a stress concentration point at the time of cleavage, that is, a weak-point, and is considered to facilitate nanominiaturization.

In order to pulp with a high copper value, it is necessary to carry out the cooking treatment under mild conditions, but due to the mild conditions, a large amount of knot lees with insufficient cooking is generated. Since the generation of a large amount of knot lees hinders the operation in the actual manufacturing equipment, it is necessary to keep the amount of knot lees generated to an operable level (generally, 5% or less by weight is ideal). is there.
According to the present invention, when bamboo is used as a raw material by using an alkaline cooking method in which the cooking proceeds more moderately, instead of the craft cooking method generally used in the production of pulp for papermaking, the alkali addition rate (AA) is used. By treating under the conditions of 17-19% (preferably 18-19%), a treatment temperature of 140-170 ° C. (preferably 155-160 ° C.), and a treatment time of 19-451 minutes (preferably 56-108 minutes). The knot rate can be suppressed to 5% or less, which allows actual operation, and the copper price can be maximized.

That is, the pulp production method for facilitating the nano-miniaturization of pulp by the defibration method using a high-pressure water stream of the present invention uses bamboo as a raw material, has a pulp copper value of 40 or more, preferably 43 or more, and is after cooking. It is characterized in that the alkaline cooking method is used under the condition that the knot ratio, which is an index of the residue, is 8% or less, preferably 5% or less.

Further, the pulp production method for facilitating the nano-miniaturization of pulp by the defibration method using a high-pressure water stream of the present invention is under cooking conditions in which the H factor is 350 or more, preferably 400 or more at an alkali addition rate of 16% or more. Optimized. The H factor referred to here is a guideline indicating the shipping cost of the heat applied to the reaction system at the time of cooking, and can be obtained by integrating from the time when the lignocellulosic material and the cooking liquid are mixed to the time when the cooking is completed. It indicates a value and is calculated by the following formula.
H factor = ∫exp (43.2-16113 / T) dt (T: absolute temperature, t: time)

Furthermore, the pulp production method that facilitates the nano-miniaturization of pulp by the defibration method using the high-pressure water flow of the present invention has a more optimum effect in the alkaline cooking method, but also in the craft cooking method after cooking. By producing pulp under cooking conditions such that the copper value of the pulp is 18 or more, preferably 21 or more, it is possible to facilitate the nano-miniaturization of pulp by the defibration method using a high-pressure water stream. become.

In the pulp production method that facilitates the nano-miniaturization of pulp by the defibration method using a high-pressure water stream by craft cooking, the H factor is 220 or more, preferably 250 or more at an alkali addition rate of 16% or more. Optimized in.

The pulp manufacturing method for facilitating the nano-miniaturization of pulp by the defibration method using the high-pressure water flow of the present invention is calculated by back calculation from the H factor regardless of whether the alkaline cooking method or the craft cooking method is used. It is further optimized by satisfying the cooking conditions of the cooking temperature of 140 ° C. or higher.

The knot rate after cooking is preferably 8% or less, preferably 5% or less as a condition that can be operated at a general manufacturing site, but this is not the case because it varies depending on the improvement of the manufacturing equipment and the increase / decrease in the processing amount. As long as the knot rate is capable of actual operation, the pulp production method that facilitates the nano-miniaturization of pulp by the defibration method using the high-pressure water flow of the present invention can be applied.

The pulp production method for facilitating nano-fine pulp by the defibration method using a high-pressure water stream of the present invention enables more optimal pulp production by using bamboo as a raw material, but the raw material is not limited to bamboo. .. As a raw material, in addition to bamboo, it can be applied to natural materials containing lignin in its constituents, such as wood and grasses.

The defibration using the high-pressure water flow of the pulp produced in the present invention is carried out by using high-pressure water of about 50 to 400 MPa with respect to the pulp made into a water mixture of 0.5 to 10% (w / w). Can be done. This can be done, for example, by using the nanocellulose production apparatus 1 shown in FIG. The nanocellulose manufacturing apparatus 1 has a pulp slurry supply path 3 which is a first liquid medium supply path arranged so that the pulp slurry can be supplied to one chamber 2, and a non-pulp slurry which is water, for example, in one chamber. It is composed of a second liquid medium supply path 4 that circulates through 2. In one chamber 2, an orifice injection unit 5 for injecting the non-pulp slurry of the second liquid medium supply path 4 in a direction intersecting the pulp slurry supply direction from the pulp slurry supply path 3 is provided. The pulp slurry supply path 3 allows the pulp slurry to be circulated through one chamber 2.

The pulp slurry supply path 3 and the second liquid medium supply path 4 have a mutual intersection 6 in one chamber 2.
The pulp slurry supply path 3 is a pulp slurry supply unit, and the tank 7 and the pump 8 for storing the pulp slurry are arranged in the circulation path 9, while the second liquid medium supply path 4 is the tank 10, the pump 11, and the heat exchanger 12. , The plunger 13 is arranged in the liquid medium supply path 4 which is a circulation path.

The non-pulp slurry is, for example, water, which is initially stored in the tank 10, and then passes through the intersection 6 with the operation of the nanocellulose manufacturing apparatus 1 to operate the nano-miniaturized pulp stored in the tank 10. Those in a state where they are to be contained at a concentration according to the degree are also comprehensively referred to.

As shown in FIG. 3, the circulation path 9 of the pulp slurry supply path 3 is arranged in a manner of penetrating the chamber 2, and the non-pulp slurry is orifice-injected in a direction intersecting the circulation path 9 so that the circulation path 9 can be penetrated. The orifice injection port 14 of the orifice injection portion 5 connected to the plunger 13 of the liquid medium supply path 4 of 2 opens inside the chamber 2. The discharge port 15 of the chamber 2 is provided at a position facing the orifice injection port 14 of the chamber 2, and the circulation path of the second liquid medium supply path 4 is connected to the discharge port 15 of the chamber 2 to form a second liquid. The medium supply path 4 is configured.

On the other hand, the circulation path 9 of the pulp slurry supply path 3 is formed by using, for example, a vinyl hose, a rubber hose, or the like, and a one-way valve 16 that is opened only in the chamber 2 direction is provided on the entry side of the circulation path 9 into the chamber 2. Can be attached. Further, a one-way valve 17 that is opened only in the discharge direction from the chamber 2 is attached to the exit side of the circulation path 9 from the chamber 2. In addition, an air suction valve 18 is attached to the circulation path 9 between the chamber 2 and the one-way valve 17, and the air suction valve 18 is opened only in the direction of sucking air into the circulation path 9 from the outside.

According to the above nanocellulose production apparatus, nanocellulose is produced as follows.
The non-pulp slurry is circulated through the chamber 2 through the second liquid medium supply path 4. Specifically, the pump 11 is used to circulate the non-alkali cooked unbleached bamboo pulp slurry in the tank 10 through the heat exchanger 12 and the plunger 13 in the liquid medium supply path 4. On the other hand, the pulp slurry is circulated in the pulp slurry supply path 3 via the chamber 2. Specifically, the pump 8 is used to circulate the pulp slurry in the tank 7 in the circulation path 9 formed by using a vinyl hose, a rubber hose, or the like.

As a result, the non-pulp slurry circulating in the second liquid medium supply path 4 is orifice-injected to the pulp slurry circulating in the pulp slurry supply path 3 and circulating in the chamber 2. Specifically, high-pressure water is supplied from the plunger 13 to the orifice injection port 14 connected to the plunger 13, and the orifice is injected from the orifice injection port 14 toward the circulation path 9 at a high pressure of about 50 to 400 MPa.

As a result, a non-pulp slurry that has passed through the through holes 26a and 26 formed in advance in the circulation path 9 formed by using, for example, a vinyl hose, a rubber hose, or the like, and has passed through the inside of the circulation path 9 in the direction intersecting the circulation path 9. Is discharged toward the discharge port 15 of the chamber 2 while entraining the pulp slurry circulating in the circulation path 9, and flows into the second liquid medium supply path 4. As a result, the non-pulp slurry circulates in the second liquid medium supply path 4 again.
In the process of repeating the above process, the pulp slurry circulating in the pulp slurry supply path 3 and circulating in the chamber 2 and the pulp in the non-pulp slurry circulating in the second liquid medium supply path 4 are gradually defibrated and used. Nanocellulose with a high degree of uniformity in defibration can be obtained.

Another method of defibrating pulp with a high-pressure water stream to obtain nanocellulose is a homogenization method in which a dispersion liquid in which pulp is dispersed in a solvent is treated with a homogenizer equipped with a crushed homovalve sheet. As shown in FIG. 4, according to this homogenization method, when the pulp 101 pumped in the homogenizer at high pressure passes through the small-diameter orifice 102, which is a narrow gap, the wall surface of the small-diameter orifice 102 (particularly, the impact ring 103 By colliding with the wall surface), it is divided by receiving a shear stress or a cutting action, and nano-miniaturization having a uniform fiber diameter is performed.

Further, as a method of defibrating pulp with a high-pressure water stream to obtain nanocellulose, there is the above-mentioned underwater facing collision method and the like, but the defibration method using a high-pressure water stream shown in the present invention is not limited to this.

According to the present invention, bamboo is used as a raw material, the copper value of the pulp is 40 or more, preferably 43 or more, and the knot ratio, which is an index of the residue after steaming, is 8% or less, preferably 5% or less. By using the alkaline steaming method, it is possible to obtain raw material pulp that facilitates nano-miniaturization of pulp by the defibration method using a high-pressure water stream.

It is a conceptual diagram of the nanocellulose production apparatus by the underwater facing collision method (ACC method). It is a conceptual diagram of an example of the nanocellulose production apparatus using the pulp obtained by the pulp production method which facilitates the nano-miniaturization of pulp by the defibration method using the high pressure water flow of this invention. It is a conceptual diagram which shows the part of the nanocellulose production apparatus shown in FIG. 2 in an enlarged manner. It is a conceptual diagram of still another example of the nanocellulose production apparatus using pulp obtained by the pulp production method which facilitates the nano-miniaturization of pulp by the defibration method using the high pressure water flow of this invention. It is a graph which shows the relationship between the fiber width of nanocellulose obtained by nanominiaturizing pulp of different copper values by the ACC method, and the copper value of raw pulp. It is a graph which shows the relationship (the cooking condition: alkaline cooking, bamboo) of the H factor and the knot rate (using a correction value) in each alkali addition rate. It is a graph which shows the relationship between the H factor and the copper value (evaporation condition: alkali cooking, bamboo) in each alkali addition rate. It is a graph which shows the relationship between the alkali addition rate and the copper value at each cooking temperature (the cooking condition: alkali cooking, bamboo). The knot dregs produced by alkaline cooking of bamboo are shown, and (a) needle-like knot dregs and (b) particle-like knot dregs are shown. Explanatory drawing which shows progress process of alkaline cooking of bamboo assumed in process of this invention It is a graph which shows the relationship between the H factor and the knot rate at the alkali addition rate of 17, 18 and 19% (melting condition: kraft cooking, bamboo). It is a graph which shows the relationship between the H factor and the copper value (cooking condition: kraft cooking, bamboo) at an alkali addition rate of 17, 18 and 19%. It is a graph which shows the relationship between the H factor and the copper value (cooking condition: kraft cooking, bamboo) at each of the alkali addition rates of 17, 18 and 19%. It is a graph which shows the comparison of the alkaline cooking and the craft cooking when the knot rate becomes 5%. Image processing example by differential interference contrast observation Differential interference contrast observation image (5-pass processed sample) Image after binarization (5-pass processed sample) Differential interference contrast observation image (30-pass processed sample) Image after binarization (30-pass processed sample) It is a graph which shows the comparison of the residual fiber amount of each sample. It is a graph which shows the comparison (graph which rearranged FIG. 20) of the amount of residual fibers of each sample. TEM image of 5-pass processed sample TEM image of a 5-pass sample (enlarged image of the square in FIG. 22). Arrows indicate single nanofibers 4-5 nm wide.

The following is a pulp production method that facilitates the nano-miniaturization of pulp by the defibration method using the high-pressure water flow of the present invention, and the ACC method, which is one of the defibration methods using the high-pressure water flow for the resulting pulp. The characteristics of nano-miniaturization behavior when miniaturized by

The cooking time was fixed at 120 minutes, and alkali cooking was carried out using bamboo chips as a raw material under the conditions of alkali addition rate (AA) of 15% and 17% and cooking temperatures of 140 ° C, 150 ° C and 160 ° C. Nanocellulose obtained when the copper value of the pulp, the amount of cooking residue (knots), and the ACC method, which is one of the defibration methods using a high-pressure water stream, were applied to the number of treatments of 5 and 30 passes. The results of measuring the fiber width of the above are shown in Table 1.

FIG. 5 shows the relationship between the kappa value of pulp subjected to nano-miniaturization and the fiber width of nanocellulose obtained by performing nano-miniaturization treatment at each treatment number, which was graphed based on the results in Table 1. .. When the number of treatments by the ACC method was 30 passes, the fiber width decreased linearly as the copper value increased. On the other hand, in the 5-pass, there was no significant change in the region where the copper value was high, but it increased sharply in the region where the copper value was low.

In the nanominiaturization of ordinary pulp for papermaking by the defibration method using a high-pressure water stream, it is necessary to cleave the bonds between nanocellulose (mainly hydrogen bonds and van der Waals forces). In the nano-miniaturization of pulp with a high copper value, which is an index of the amount of residual lignin, the stress concentration point when the lignin remaining (spotted) in the pulp cleaves the bond between nanocellulose, that is, Week-point. It is thought that it will be. However, in a state where the value of the kappa value is small and the amount of residual lignin is small, it is considered that the Week-point at the time of nano-miniaturization is small, and as a result, it is difficult to nano-fine, and the fiber width of the obtained nanocellulose is high. Especially in the initial stage of nano-miniaturization (low pass region), the influence is strong, and it is considered that the kappa value has a strong influence on the fiber width as in the case of the 5-pass treatment in FIG.

That is, in the nano-miniaturization of pulp by the defibration method using a high-pressure water stream, the one with a higher copper value of the pulp as a raw material, that is, the one with a large amount of residual lignin, can be more easily miniaturized. Shown.
However, under cooking conditions with a high copper value, the knot rate was high, and it was a harsh condition for actual operation (ideally, the knot rate was 5% or less).

Therefore, in order to find a condition where the knot rate is 5% or less and the copper value is maximized, the cooking time is fixed at 120 minutes, the alkali addition rate (AA) is 17%, 18%, 19%, and the cooking temperature is 140. Alkaline steaming using bamboo chips as a raw material was carried out under the conditions of ° C., 150 ° C. and 160 ° C., and the copper value of the pulp obtained after the cooking and the amount of the cooking residue (knots) were compared. Table 2 shows a list of the results. Here, in order to unify the different cooking conditions, the "H factor" calculated from the cooking temperature and the cooking time was calculated under each condition, and the kappa value with respect to the H factor and the knot rate with respect to the H factor were graphed in each AA. The results are shown in FIGS. 6 and 7.
The H factor here is a guideline for the total amount of heat applied to the reaction system during cooking, and is calculated by integrating from the time when the lignocellulosic material and the cooking liquid are mixed to the time when the cooking liquid is completed, according to the following equation. can get.
H factor = ∫exp (43.2-16113 / T) dt (T: absolute temperature, t: time)

From FIG. 6, it was clarified that the knot rate decreased as the H factor increased, and that the knot rate generated as the AA increased even with the same H factor decreased. From this result, in order to satisfy the knot rate of 5% that can be actually operated, the H factor is 758 or more at AA = 17%, the H factor is 507 or more at AA = 18%, and the H factor is 437 at AA = 19%. It was suggested that this is necessary.
Further, from FIG. 7, it was clarified that the kappa value decreased as the H factor increased, and that the kappa value decreased as the AA increased even with the same H factor. From this result, the values of H factor and copper value in each AA that satisfies the knot rate of 5% that can be actually operated and the kappa value is maximized are as follows: AA = 17%, H factor is 758, copper value is 36, AA = It was suggested that at 18%, the H factor was 507 and the kappa value was 43, and at AA = 19%, the H factor was 437 and the kappa value was 43.

In FIG. 8, the relationship between the alkali addition rate and the copper value of the pulp obtained when the pulp was steamed at each cooking temperature was plotted from the results of Tables 1 and 2. At a cooking temperature of 140 ° C., the decrease in kappa value peaked at AA = 17-18% or more, but decreased at a rate of 1.5 points per AA = 1% at AA = 17% or less. On the other hand, at a cooking temperature of 160 ° C., the rate decreased at a rate of 2.4 to 2.6 points, indicating that the higher the cooking temperature, the greater the decrease in the kappa value even with the same change in the alkali addition rate.

The alkali added in the cooking functions to elute the lignin in the chip. Lignin in the chip is present in various parts of the hierarchical structure of the plant cell wall, but under mild conditions, lignin elution between pulps (intercellular layer) is prioritized over lignin elution in pulp (secondary wall). It is thought that. The amount of decrease in copper value between AA = 17% -18% at 140 ° C and 150 ° C is 1.4 to 1.5 points per AA = 1%, but between AA = 18% -19% at 150 ° C, 1. It has risen to 8 points, and at 160 ° C, it has risen further to 2.4 to 2.6 points. That is, under the condition of AA = 18% or less at 150 ° C., the added alkali mainly acts on the elution of lignin between pulps, and under the condition of AA = 18% or more at 150 ° C., it is added between pulps and from inside the pulp. It is considered that lignin elution is large.

FIG. 9 is a photograph of knot dregs generated by alkaline cooking of bamboo. Two types of knot dregs were observed. One is a needle-shaped knot lees as shown in FIG. 9 (a), which is a normal knot lees often found in kraft cooking of wood. The other is the particulate knot lees as shown in FIG. 9 (b), which is not found in wood. This knot lees (b) is considered to be a knot lees peculiar to bamboo because it can be seen not only in alkaline steaming but also in craft steaming.

The knot rates of the samples steamed at 160 ° C. were AA = 17%, 18% and 19%, respectively, 5.0%, 3.3% and 2.4%, respectively. Looking at the knot dregs generated at this time, there are almost no needle-shaped knot dregs (Fig. 9 (a)) as seen at other cooking temperatures, but only particle-like knot dregs (Fig. 9 (b)). It was.

Even when steamed under other conditions, the knot meal in FIG. 9 (a) tended to decrease as the knot rate decreased, but the knot meal in FIG. 9 (b) was tested regardless of the knot rate. Almost the same amount remained under all conditions (visual observation, not accurate weighing). Further, as described above, there was almost no knot meal shown in FIG. 9 (a) in the knot meal steamed at 160 ° C., and only the knot meal shown in FIG. 9 (b) was present. This suggests that the knot dregs in FIG. 9B are very difficult to evaporate, but are easily detached from the chips.

From the above, as the alkaline cooking process of bamboo, the progress process as shown in FIG. 10 can be considered. First, in the initial stage of cooking, lignin between pulps (intercellular layer lignin) is preferentially eluted, and lignin (secondary wall lignin) in the pulp is less eluted. As the intercellular layer lignin decreases (mid-cooking), the elution of secondary wall lignin increases. When the intercellular layer lignin is almost eliminated and the needle-shaped knot lees (FIG. 9 (a)) is eliminated, only the elution of the secondary wall lignin proceeds and the kappa value decreases. It is considered that the particulate knot meal (FIG. 9 (b)) is generated from the initial stage of cooking and remains almost unchanged until the end of cooking. In other words, since particulate knot meal (Fig. 9 (b)) that is extremely difficult to evaporate remains, the knot rate does not easily become zero even if the cooking conditions are strengthened, and only the elution of secondary wall lignin progresses. It is conceivable to do.

That is, it can be said from the above consideration of the alkaline cooking process that even if the H factor is increased in order to reduce the knot rate, the decrease in the kappa value occurs preferentially over the decrease in the knot rate.

In the nano-miniaturization of pulp by the defibration method using high-pressure water flow, it is considered that the higher the copper value, which is an index of residual lignin, the easier the nano-miniaturization progresses, so the knot rate is 5% or less. In order to facilitate nanominiaturization, the conditions of AA = 18% and 19% are better than the conditions of "AA = 17%, H factor 758, copper value 36" obtained in the examination of the conditions. , More preferable.

Comparative Example 1

The present invention has been studied using an alkaline cooking method, which is not currently the mainstream, for the purpose of increasing the kappa value after cooking. The results of a similar comparative study using the kraft cooking method currently used for general pulp production will be described below.

Using the same bamboo chips used in the study of alkaline cooking as raw materials, pulping was carried out by the craft cooking method by changing the alkali addition rate (AA), cooking temperature, and cooking time, and the copper value and knots of the obtained pulp were obtained. The relationship between the rate and the H factor was derived. The results are shown in FIGS. 11 and 12.

From FIG. 11, it was clarified that the knot rate decreased as the H factor increased, and that the knot rate generated as the AA increased even with the same H factor decreased. From this result, in order to satisfy the knot rate of 5% that can be actually operated, the H factor is 835 or more at AA = 17%, the H factor is 399 or more at AA = 18%, and the H factor is 320 at AA = 19%. It was suggested that this is necessary.
FIG. 12 shows the relationship between the H factor and the copper value. However, in the approximate expression obtained from the graph, the approximate curve is drawn as shown in FIG. 13 because the deviation between the measured value and the approximate curve is large. From the relational expression obtained from the correction, the values of H factor and copper value in each AA that satisfied the knot rate of 5% that can be actually operated and maximized the copper value were derived. As a result, when AA = 17%, the H factor is 835 and the kappa value is 18.1, when AA = 18%, the H factor is 399 and the kappa value is 21.1, and when AA = 19%, the H factor is 320 and the kappa value is 18. It was suggested to be 21.0.

The results obtained from the above examination were compared with the results of the alkaline cooking test (Fig. 14). The H factor when the knot rate is 5% is lower in alkaline cooking at low alkali addition rate, but it reverses at AA = 17-18%, and it is lower in craft cooking at AA = 18% or more. It was. It was clarified that the kappa value when the knot rate was 5% was lower in the kraft cooking at any alkali addition rate, and the lignin removal was promoted in the kraft cooking than in the alkaline cooking.

In other words, in the nano-miniaturization of pulp by the defibration method using high-pressure water flow, the higher the copper value, which is an index of the amount of lignin remaining in the pulp after cooking, the easier it is to miniaturize the pulp. It was suggested that the pulp obtained by the kraft cooking method, which cannot maintain the copper value of the pulp after cooking higher than that of the alkaline cooking method, is unsuitable.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following description.

The pulp cooking conditions that facilitate the nano-miniaturization of pulp by the defibration method using the high-pressure water flow obtained in the above study were examined by the H factor that does not limit the cooking temperature and cooking time. Therefore, Table 3 shows a list of cooking conditions in the alkaline cooking method in which the cooking temperature and cooking time were determined by back calculation from this H factor, and Table 4 shows a list of cooking conditions in the craft cooking method.

Of the cooking temperature and cooking time shown in Tables 3 and 4 obtained by back calculation from the H factor, the condition that the cooking time is too long or too short is not realistic when the general actual operation is taken into consideration. Further, in the nano-miniaturization of pulp by the defibration method using a high-pressure water stream, the higher the kappa value, which is an index of the amount of lignin remaining in the pulp after cooking, the easier it is to miniaturize the pulp. , Five conditions were selected from the conditions shown in Table 4, and laboratory cooking was carried out by each cooking method under these five conditions. However, since it was assumed that the kappa value of kraft cooking was lower than that of alkaline cooking and it was difficult to nanonize it, a test was conducted when examining Comparative Example 1 under almost the same conditions as the condition of AA = 19% in Table 4. Pulp was used as a representative.
Table 5 shows these five conditions and the test results obtained by steaming under those conditions.

The results of laboratory cooking shown in Table 5 almost satisfied the condition that the kappa value was maximized at the "knot rate of 5% or less" estimated by the study, thus indicating the validity of the above study results.

The pulp shown in Table 5 obtained in Example 1 was subjected to a defibration method using a high-pressure water stream under the conditions of a treatment concentration of 0.05% (w / w), an ejection pressure of 200 MPa, a number of treatments of 5 passes and 30 passes. Each nanocellulose-dispersed water was obtained by subjecting each to one ACC treatment.
Since the pulp subjected to the ACC treatment was close to the upper limit satisfying the knot rate of 5% or less, a large amount of fine knot residue that had passed through the knot screen remained. Since the chamber nozzle diameter of the ACC machine is as small as φ160 μm, this knot meal immediately clogged and could not be processed. Therefore, a large knot meal was manually removed from the pulp suspension water before being subjected to ACC using tweezers, and then subjected to ACC treatment.

By evaluating the nanocellulose in each of the obtained nanocellulose-dispersed water and the micro-sized fibers with insufficient defibration, the nano-miniaturization by the defibration method using the high-pressure water flow of the pulp obtained under each condition is performed. "Easiness to be done" was compared and examined.

The sample to be evaluated is in a "non-uniform state" in which the number of ACC treatments is as small as 5 passes, many undissolved microfibers are present, and the fiber width distribution of the finely divided nanofibers is broad. Therefore, the comparison of fiber widths by ordinary TEM observation shows a great deal of variation, and it is difficult to make an appropriate evaluation. Therefore, instead of evaluating with the obtained "nanofiber", we tried to evaluate by comparing the residual state of "microfiber" with insufficient defibration.

The slide prepared by dropping each nanocellulose-dispersed water onto a slide glass was photographed in the differential interference contrast observation (100 times, monochrome) mode, and the color balance was adjusted to make the black and white clearer. The image was captured by Image J, binarized with a certain threshold value, and then the area of the fiber portion was obtained and compared. For the purpose of reducing the measurement error, 100 images were linked to one image by using the image linking function, so that the observation was performed in as wide a range as possible. The size of the image used for image processing is calculated from the scale bar (about 6 mm x 8 mm), and exists at the measurement location from the area ratio with the cover glass (18 mm x 18 mm), the amount of sample dropped during preparation, and the sample concentration. The fiber weight was determined, and the obtained fiber area was converted into the measured area per sample weight for comparison.

As a typical example, it will be described below using an observation image before image connection (FIG. 15). FIG. 15a) is an image of the fiber acquired by a normal observation method. Relatively large fibers can be identified, but fibrilized end fibers are difficult to identify. However, in FIG. 15b) observed with a differential interference light microscope, even the fine fibers at the ends can be confirmed. An image in which the color balance of this image is adjusted is shown in FIG. 15c). By performing this treatment, the lightly reflected dust and unevenness were blackened and the fibers were clarified. Since the image at this stage is an image having monochrome black-and-white gradation, it was binarized by setting a certain threshold value using image processing software (Image J) (FIG. 15d). As a result, the image is converted into two colors, white and black. After that, the area of the black part corresponding to the fiber presence location was calculated. As the preparation used for the observation, a pipetter with a cut tip was used, and an amount of the sample dropped on the slide glass did not protrude from the cover glass (about 0.01 g). The dropping amount of each sample was recorded with a precision balance. After preparation, the edges of the cover glass were sealed with nail polish to prevent solvent evaporation and fiber transfer to the cover glass edges. Then, an image of an arbitrary part excluding the edge of the cover glass was taken and subjected to the above processing. The observation was carried out using Lieca's inverted microscope DMi8 under the observation conditions using the differential interference contrast microscope shown in Table 6. The image processing was performed using the free software Image J under the image processing conditions shown in Table 7.

The differential interference contrast observation image and the binarized image of each sample are shown in FIGS. 16 to 19 (FIGS. 16 and 17 are 5-pass processed samples, and FIGS. 18 and 19 are 30-pass processed samples). In the 5-pass treated sample, many undefibrated fibers having a fiber length of several mm were present, and in A-2, A-4, and K-1, the amount seemed to be large (FIGS. 16 and 16). 17). In particular, K-1 had a longer fiber length and a larger amount than the others. On the other hand, in the 30-pass processed sample, almost no large fibers as seen in the 5-pass processed sample remained, and fibers having a reduced width and length existed in a lump shape (FIG. 18, FIG. 19). The lump-shaped fiber lumps tended to be less in the kraft cooking sample (K-1) and more in the alkaline cooking sample (A-1 to 4).

FIG. 20 shows a comparison of each sample by converting the area of the fiber portion measured by binarizing the image into the area per 1 g of all the fibers existing therein. The obtained numerical values show almost the same tendency as the appearance of the image, and it is judged that the amount of residual fibers is appropriately quantified by this method. The amount of residual fibers of A-1 and A-3 in the 5-pass treated sample was less than half of the other, and it was clarified that these samples were miniaturized in a lower pass than the others. The amount of residual fiber in the 30-pass treated sample was not as different as that in the 5-pass treated sample, but K-1 was less than the others.

FIG. 21 shows a graph in which the graph of FIG. 20 is rearranged in order from the smallest value of the 5-pass processed sample. It can be seen that the amount of residual fiber in the 5-pass processed sample is smaller in the sample having a low cooking temperature and in the alkaline cooking. Comparing the values of the amount of residual fibers in the 5-pass processed sample and the 30-pass processed sample, there is no significant difference between A-1 and A-3, but the residual fibers are found in A-2, A-4, and K-1. It can be seen that there is a large decrease from 5 passes to 30 passes.

Since the "residual fiber" measured by this measurement depends on the raw material pulp, it decreases as the number of ACC treatments increases, as in A-2, A-4, and K-1. However, in A-1 and A-3, since the values of the remaining fiber amount of the 5-pass processed sample and the 30-pass processed sample hardly change, it is considered that the miniaturization in the micro size has already been completed at the time of 5 passes. Be done. That is, it seems that a dramatic decrease in the amount of residual fiber as seen in A-2, A-4, and K-1 occurred between 1 to 5 passes. From this, it is considered that A-1, A-3 was a sample that was "easier to nanonize" than A-2, A-4, and K-1.

The examination of the ease of nano-miniaturization based on the amount of residual fibers performed in the differential interference contrast observation mode of an optical microscope is a so-called indirect evaluation comparing "residual states of microfibers with insufficient defibration". Therefore, it is necessary to confirm the state of the nanofibers that have actually been nano-sized.

Therefore, the 5-pass processed samples of each sample were subjected to TEM observation and the states of the nanofibers were compared (FIGS. 22 and 23). Since many single nanofibers having a fiber width of about 4 to 5 nm were observed in all the samples (Fig. 23), it was confirmed that nanominiaturization occurred even in 5 passes.

107 ... Chamber, 108a, 108b ... Nozzle, 109 ... Tank, 110 ... Plunger, 111 ... Heat exchanger.

Claims (2)

Alkaline steaming that facilitates nano-miniaturization of pulp by a defibration method using a high-pressure water stream, which is characterized in that the copper value of the raw material pulp is 40 or more and the knot ratio after cooking is 8% or less. Pulp production method by solution method. The pulp production method according to claim 1, wherein the raw material is bamboo.

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