JP2018003172A - Method for micronizing kenaf cellulose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for micronizing kenaf cellulose that not only can decrease the amount of a chemical liquid in a cooking step but also can shorten the cooking period of time and facilitates handling after the cooking step.SOLUTION: The method for micronizing kenaf cellulose comprises a washing step, a dewatering step, a drying step, a crushing step of crushing into a size of 6 to 8 mm by a dry type crushing, a pulverizing step of pulverizing into a size of 1 to 3 mm by a dry type pulverization, a cooking step, a solid-liquid separation step of separating a liquid substance from the cooked cellulose in the cooking step, a micronization step of micronizing by a wet type stone mill type crusher, a bleaching/hydrophobilization step of bleaching and hydrophobilizing using a bleaching agent and a surfactant, a washing/dewatering step of washing and dewatering, a granulation step of pelletizing and a drying step of drying the pelletized cellulose.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for refining kenaf cellulose.

In recent years, the recycling and re-commercialization business has become active and the use of recycled resources has begun to take root. Even in the resin industry, recycling and recycling are active. At present, we are seeking to improve the quality of recycled resin by improving the physical properties of the recycled resin and seeking a more advanced recycled resin.
Much research and development has been conducted on the utilization of cellulose, and improvement of modification by mixing and compatibilization of cellulose and resin is being attempted.
For example, Patent Documents 1 to 5 disclose a method of mixing cellulose with a resin.
Patent Document 1 includes a cutting step for cutting raw material fibers, and a mixing step for kneading and mixing the thermoplastic resin and the cut fibers, so that a large amount of plant fibers can be contained, and injection molding, etc. Has proposed a method for producing a thermoplastic resin composition having sufficient fluidity when used.
Patent Document 2 is a cutting step in which plant fibers are cut into a predetermined length (preferably the fiber length is 20 mm or less), and the cut fibers are ground fibers having a predetermined size (preferably an average fiber length is 0.5 to 6 mm. And a mixing step of melt-kneading and mixing the thermoplastic resin and the pulverized fiber, so that a large amount of plant fiber can be contained and injected. A method for producing a thermoplastic resin composition having sufficient fluidity when used in molding or the like has been proposed.
Patent Document 3 discloses a step of mixing a thermoplastic resin (PP or the like) with a plant material (kenaf or the like) to obtain a first mixture containing 50 to 95% by mass of a plant material, and a thermoplastic resin ( PP, etc.) is mixed with plant material (kenaf, etc.) to contain 50-95 mass% plant material, flexural modulus is 50-90% of the first mixture, and bar flow length is first. A step of obtaining a second mixture 1.1 to 2.5 times the mixture, a third mixing step of obtaining a mixed crushed product of a first crushed product obtained by crushing the first mixture and a second crushed product obtained by crushing the second mixture, and mixing A method for producing a thermoplastic composition and a molded body, which are provided with a pelletizing step for pelletizing a crushed material, so that a molded body excellent in injection properties and mechanical properties can be obtained while containing a large amount of plant material. The manufacturing method is proposed.
Patent Document 4 includes a mixing step in which a thermoplastic resin and plant fiber are kneaded and mixed to form a resin fiber mixture, and a rolling step in which the resin fiber mixture is rolled to obtain a flat rolled product C1. A method for producing a thermoplastic resin composition that can contain a large amount of plant fiber and has sufficient fluidity when used for injection molding or the like has been proposed.
Patent Document 5 discloses a steaming process in which a plant material (kenaf core) is steamed, a pelletizing process in which the steamed plant material is pressed to obtain a plant material pellet, a plant material pellet and a thermoplastic resin (polypropylene and And / or polylactic acid) to provide a thermoplastic resin composition in this order, so that the thermoplastic resin composition can be mixed efficiently even if the specific gravity difference between the plant material and the thermoplastic resin is large. The manufacturing method of this and the manufacturing method of a molded object are proposed.
Patent Document 6 proposes a fiber-reinforced resin composition suitable for manufacturing a molded product such as an electric / electronic device product by setting the content of kenaf fiber to 10 to 50% by mass.
Patent Document 7 is a biodegradable resin composition that is a thermoplastic resin having crystallinity, and by setting the content of kenaf fibers to 10 to 50% by mass, it can be used for molded products such as electrical and electronic equipment products. A fiber reinforced resin composition suitable for production is proposed.
Patent Document 8 is a thermoplastic composition containing at least 50% by weight or more of non-wood fibers as natural fibers. Particularly, the non-wood fibers are kenaf pulp, which is excellent in dimensional stability and disposal characteristics, and has no odor. A plastic composition is proposed.
By the way, in order to contain cellulose in the resin composition, the cellulose to be mixed is as fine as possible (micron unit or more), the cellulose at the time of mixing is dispersed as much as possible, and mixing with the resin melts from the time of mixing. Long-term uniform mixing is necessary.
Here, as a method for refining cellulose, there are dry, wet, and chemical refining.
Patent Document 9 describes a shear force in a direction perpendicular to the long axis of a fiber in a suspension medium under a concentration condition in which the suspension has thixotropic properties under a medium in which natural organic fibers are swollen. Under a condition where the liquid is added, the suspension can be guided between two rotating desks, and ultrafine defibration can be obtained. The diameter is several nanometers (several nm) to several tens of nanometers (several tens of nanometers). We propose ultra-fine fibers made of As a specific method, a central portion between two rotating desks (two desks rotating in opposite directions) is prepared by dispersing a suspension of the fibers in water or a solution that swells natural organic fibers. Or when one of the two is fixed and the other rotates in the center between the two desks, and the suspension moves outward from the center due to the centrifugal force generated by the desk rotation. The long axis direction is guided to coincide with the centrifugal force direction.
In Patent Document 10, a suspension of fibrous cellulose is cut by passing through a small-diameter orifice, giving the suspension a high speed with a pressure difference of at least 3000 pii, and then colliding it and rapidly decelerating. And a step of repeating this step to make the cellulose suspension a substantially stable suspension, which substantially changes the chemical starting material of the cellulose. We have proposed a method for producing a microfibrous cellulose that converts the cellulose to a microfibrous cellulose without causing any problems. In Patent Document 10, a ball mill is used to produce cellulose having a diameter of several tens of microns. The chemical bonding of cellulose is broken by the ball milling process, and the cellulose is pulverized by pressurizing it in water. To obtain fine cellulose having a particle size of 1 micron or less, in the case of a cellulose derivative, pulverize it in liquid nitrogen, or pulverize it with a sound wave using a ball mill. It is described to make.
Patent Document 11 includes a fixed whetstone obtained by combining a natural fiber material raw material in which 10 to 15 times the amount of water or oil is mixed with 1 part by weight of natural fiber with an upper polymer, and a rotary whetstone that is combined with the lower polymer. Are in contact with each other on the flat surface of the circumferential part, and the upper and lower surfaces sandwich grinding ridges and concave grooves inclined in opposite directions with respect to the radial direction on the inner concave surface of the inner peripheral part following the circumferential flat surface. By supplying the central part between the fixed grindstone and the rotating grindstone of the crusher arranged so as to cross in a shape, the centrifugal force accompanying the rotation of the rotating grindstone and the contact between the grinding ridges of the upper and lower grindstones, It has been proposed to obtain a natural fiber body defibrated to a diameter of 0.9 μm or less from the outer peripheral discharge part between the grinding stones by repeatedly applying shearing and grinding of the fiber raw material within 10 times.
In Patent Document 12, a kenaf solution preparation step of preparing a kenaf solution by dissolving a kenaf-derived polymer in a solvent and an electrospinning step of performing electrospinning using an electrospinning solution containing the kenaf solution are performed in this order. Has proposed.
Patent Document 13 discloses a first step in which a raw material fibrous material (for example, cellulose) is dispersed in a medium (for example, water) and treated with a high-pressure homogenizer to obtain a microfibrylated suspension of the fibrous material, The suspension is drained (for example, by filter press dehydration) to form a solid cake, and the cake-like substance is crushed to a convenient level and moistened with a liquid medium. Nonetheless, the microfiber material is produced by the third step, which is a non-adhesive, and does not block even when the packaged material is stacked and can be handled as a substantially fine particle material. Propose to manufacture.
In Patent Document 14, a wood chip is hydrophilized at room temperature using a dilute caustic soda solution, and the lignin is selectively oxidized by partial oxidation in dilute nitric acid, and digested under atmospheric pressure using a dilute caustic soda solution. To produce pulp.
Patent Document 15 includes an enzyme treatment step in which an enzyme is allowed to act on the bast of a plant in the presence of water. By including pectinase in the enzyme, plant fibers can be produced from the plant in a simple environment. A method for producing plant fibers is proposed.
Patent Document 16 is a natural fiber manufacturing method including a letting treatment step in which fibers are unwound by a letting treatment in which the fiber plant material is immersed in a defibrating solution containing microorganisms that decompose substances existing between the fibers of the fiber plant material. It has been proposed to reduce the peculiar odor generated in the natural fiber after the letting treatment by having a pressure boiling step in which the fiber subjected to the letting treatment through the letting treatment step is pressurized and heated in water.

JP 2010-275400 A JP 2010-241986 JP 2010-30047 gazette JP 2011-5742 A JP 2009-96875 JP 2011-63821 A JP 2005-105245 JP JP 2000-219812 JP JP 2003-155349 A JP-A-56-19921 JP-A-4-281017 JP 2013-44063 A JP-A-3-152130 JP 2009-167554 A JP 2013-91878 A JP 2010-47849 A

  As described above, methods for refining cellulose include dry, wet, and chemical refining, but it is important that processing before and after, storage, and movement can be easily performed at low cost.

  An object of the present invention is to provide a method for refining kenaf cellulose that can reduce the amount of a chemical solution in the cooking process and shorten the cooking time, and is easy to handle after the cooking process.

The method for refining kenaf cellulose according to claim 1 of the present invention includes a washing step for washing the introduced kenaf, a dehydration step for dehydrating the kenaf washed in the washing step, and the kenaf dehydrated in the dehydration step. A drying step for drying, a crushing step for crushing the kenaf dried in the drying step to 6 mm to 8 mm by crushing by a dry method, and crushing the kenaf crushed by the crushing step to 1 mm to 3 mm by crushing by a dry method A crushing step, a cooking step in which the kenaf crushed in the crushing step is digested with a chemical liquid mainly composed of caustic soda and sodium sulfide, and a solid-liquid separation in which a liquid is separated from the cellulose digested in the cooking step Step and refinement step of refining the cellulose separated in the solid-liquid separation step by wet millstone mill after washing and dehydration The cellulose refined in the refinement process is bleached and hydrophobized using a bleaching agent and a surfactant, and the cellulose hydrophobized in the bleaching and hydrophobizing process is washed. A dehydrating step for dehydrating, a granulating step for pelletizing the cellulose dehydrated in the washing and dehydrating step by a pelletizer, and a drying step for drying the cellulose pelletized in the granulating step. Features.
The present invention according to claim 2 is the pulverization method of kenaf cellulose according to claim 1, wherein the cellulose that has been washed and dehydrated in the washing and dehydrating step is wetted before the granulation step. And after the ultrafine process, a mixing and stirring process in which the first substance having a specific gravity of 1 or less and the cellulose are stirred with a solvent, and after the mixed and stirred process, mixing And a dehydrating step of dehydrating the first substance and the cellulose by a laminating method, and the granulating step is performed after the laminating and dehydrating step.
The present invention described in claim 3 is the pulverization method of kenaf cellulose according to claim 1, wherein the cellulose that has been washed and dehydrated in the washing and dehydrating step is wetted before the granulation step. And a step of mixing the cellulose with a second substance having a specific gravity greater than 1 after the ultrafine step, and the granulation step after the step of mixing. It is characterized by performing.

  According to the present invention, since the kenaf is appropriately refined by two-stage dry pulverization before the cooking process, the amount of chemical in the cooking process can be reduced and the cooking time can be shortened. Since it has not been refined, it is easy to handle after the cooking step. In addition, according to the present invention, generation of mold can be prevented by using a bleaching agent, and kenaf can be hydrophobized by using a surfactant, so that it is necessary to store and move in a state dispersed in water. It can be stored and moved in pellet form.

Process drawing by the refinement | miniaturization method of kenaf cellulose by one Example of this invention.

  The method for refining kenaf cellulose according to the first embodiment of the present invention includes a washing step for washing the introduced kenaf, a dehydration step for dehydrating the kenaf washed in the washing step, and drying the kenaf dehydrated in the dehydration step. Drying process, crushing process for crushing kenaf dried in the drying process to 6 mm to 8 mm by crushing by dry process, crushing process for crushing kenaf crushed by crushing process to 1 mm to 3 mm by crushing by dry process, and crushing process The kenaf crushed in step 1 is cooked using a chemical solution mainly composed of caustic soda and sodium sulfide, and the solid-liquid separation step for separating the liquid material from the kenaf cooked in the cooking step, and the solid-liquid separation step. The refined cellulose is refined by a wet millstone mill after washing and dehydration, and the cellulose refined by the refinement process is used for the bleaching agent and the surface activity. Pelletizer for bleaching / hydrophobizing process using hydrophobicity agent, bleaching / hydrophobing process for bleaching / hydrophobizing cellulose, washing / dehydrating process for washing / dehydrating cellulose, and washing / dehydrating cellulose for washing / dehydration process And a granulating step of pelletizing by the step of drying, and a drying step of drying the cellulose pelletized in the granulating step. According to the present embodiment, since the kenaf is appropriately refined by two-stage dry pulverization before performing the cooking process, the amount of chemical in the cooking process can be reduced and the cooking time can be shortened. Since it is not made ultrafine, it is easy to handle after the cooking step. In addition, according to the present embodiment, generation of mold can be prevented by using a bleaching agent, and cellulose can be hydrophobized by using a surfactant, so that it can be stored and transferred in a state dispersed in water. There is no need to do this, and it can be pelletized for storage and transportation.

  According to the second embodiment of the present invention, in the kenaf cellulose refinement method according to the first embodiment, the cellulose that has been washed and dehydrated in the washing and dehydration step is subjected to a wet millstone mill before the granulation step. Ultra-fine process to make ultra-fine, mixed stirring process for stirring cellulose and first substance having specific gravity of 1 or less after ultra-fine process, and mixed first substance after mixing and stirring process And a dehydration step of dehydrating cellulose and cellulose by a laminating method, and a granulation step is performed after the dehydration step. According to the present embodiment, homogeneity with the first substance having a specific gravity of 1 or less can be achieved.

  The third embodiment of the present invention is a method for refining kenaf cellulose according to the first embodiment, wherein the cellulose that has been washed and dehydrated in the washing and dehydration step is subjected to a wet millstone mill before the granulation step. It has an ultra-fine process for making ultra-fine, and a mixing process for mixing cellulose with a second substance having a specific gravity greater than 1 after the ultra-fine process, and the granulation process is performed after the mixing process. . According to the present embodiment, it is possible to achieve homogeneity with the second substance having a specific gravity greater than 1.

Hereinafter, a method for refining kenaf cellulose according to an embodiment of the present invention will be described.
FIG. 1 is a process diagram of a method for refining kenaf cellulose according to an embodiment of the present invention.

  Kenaf (scientific names: hibiscus cannabinus and hibiscus sabdariffa, etc.) according to this example is called red hemp, cuban kenaf, western hemp, taikenaf, mesta, bimli, ambari, bombay, etc., and epidermis and woody stem (vascular bundle) It is a plant classified as a mallow family. Other than kenaf, annual plants having cottony stems (vascular bundles) such as tomatoes (scientific name: Solanum lycopersicum) and sunflowers (scientific name: Helianthus annuus) can be used.

The process from the carrying-in process in step 1 shown in FIG. 1 to the solid-liquid separation process in step 9 is a kenaf pulping process.
In the carrying-in process in step 1, a kenaf cut-off product cut and wound into a roll is carried.

  In the cleaning process in Step 2, after the unpacked kenaf wound in the roll shape is loaded, it is put into a belt contour for cleaning.

  A sorting process is performed together with the cleaning process in Step 2 or after the cleaning process in Step 2 (Step 3). In the sorting process in step 3, soil and mud other than kenaf are removed from the washed kenaf.

  After the selection process in step 3, a dehydration process is performed (step 4). For the dehydration process in Step 4, a screw press is used. The screw type press machine is a press machine that converts a rotational movement of power such as a motor into a reciprocating movement by a screw mechanism. Depending on the method of transmitting the rotational motion to the screw mechanism, there are a friction press machine through a friction clutch and a servo press machine that directly drives the screw mechanism with a servo motor.

  After the dehydration process in step 4, a drying process is performed (step 5). For the drying process in Step 5, a heating drum dryer is used. A heated drum dryer is a continuous drum that attaches dry matter to the surface of a cylindrical drum, supplies steam or warm water as a heat medium inside the drum, and performs drying while contacting the drum in the form of a surface film. Can do. Drying with a heating drum can prevent cinnamon from remaining during crushing.

  A crushing process is performed after the drying process in Step 5 (Step 6). In the crushing process in Step 6, the kenaf is crushed into a size of 6 mm to 8 mm with a dry uniaxial crusher. The kenaf is crushed so as to be cut by a rotary blade attached to the rotating rotor and a fixed blade attached to the main body. The crushed kenaf passes through a screen attached to the uniaxial crusher main body and is discharged from the lower part of the main body. The kenaf that cannot pass through the screen is crushed again until it reaches a size that can pass through the screen. Further, the kenaf is introduced from above by the hopper and pushed by the pusher, so that crushing is stably continued. By the crushing process in Step 6, the size suitable for the crushing process in Step 7 can be obtained.

After the crushing process in Step 6, a crushing process is performed (Step 7). In the pulverization step in Step 7, the primary crushed product (6 mm to 8 mm) is pulverized to a size of 1 mm to 3 mm by a dry hammer mill. The hammer mill is a high-speed rotary pulverizer, and impacts the supplied particles with a hammer that rotates at high speed and pulverizes. The hammer has a swing hammer type. By placing a perforated plate, screen, grit, etc. on the outlet side, the particle size of the pulverized product can be controlled as a so-called screen mill.
The finer the particle size of the crushed kenaf, the easier it is to digest, but if it is pulverized too finely, handling in the subsequent process is not easy.

The cooking process is performed after the pulverization process in Step 7 (Step 8). In the cooking step in Step 8, kenaf is cooked using a chemical solution mainly composed of caustic soda and sodium sulfide. The cooking step is preferably performed at a high temperature.
The finer the particle size of the kenaf pulverized in the pulverization step in Step 7, the shorter the amount of chemical used for the reaction and the stew time.

  A solid-liquid separation process is performed after the cooking process in Step 8 (Step 9). In the solid-liquid separation step in Step 9, in order to separate the pulp (cellulose) and the boiled liquor, the pulp is put into a bag of hemp or the like, and the resin liquid (commonly called black liquor) is squeezed out from the pulp by pressing under pressure. As long as the moisture content of the pulp is 20 to 30% or less, the pulp may not be completely dehydrated solid-liquid separation. The pulp from which the resin liquid has been separated is washed again with water, dehydrated and celluloseized.

The process from the refinement process in Step 10 to the drying process in Step 18 is a cellulose pelletization process.
In the refinement process in step 10, the refinement process is performed using a wet milled stone mill with a high rotational speed. The pulverizer is preferably a wet type in order to cool the heat generated by grinding by rotation. The cellulose is refined to 10 to 60 nm by the refinement process in Step 10.

  After the miniaturization process in step 10, a bleaching / watering process is performed (step 11). In the bleaching / flooding step in step 11, bleaching is performed using a chlorine-based bleaching agent in order to prevent the generation of mold fungi on the refined cellulose. In addition, a surfactant is used for flooding.

  After the bleaching / flooding process in step 11, a washing and dehydrating process is performed (step 12). In the washing and dewatering step in step 12, the bleached and submerged cellulose is washed and dehydrated.

  After the cleaning and dehydrating process in step 12, an ultrafine process is performed (step 13). In the ultrafine refinement process in Step 13, ultrafine refinement processing is performed using a wet millstone type pulverizer. Using a mortar-type pulverizer with high wet rotation speed, the kenaf fiber is made ultrafine by simultaneously performing pulverization and dusting. By the ultrafine process of step 13, cellulose is ultrafinened to 10 nm to 30 nm.

  When the first substance having a specific gravity of 1 or less is mixed, the mixing and stirring process is performed after the ultrafine process in step 13 (step 14). In the mixing and stirring step in Step 14, the first substance having a specific gravity of 1 or less and cellulose are stirred with a solvent. For example, mixing and stirring in water. Here, the first material with a specific gravity of 1 or less is a material that can be used as a new material.For example, there are polypropylene and polyethylene, and by kneading the resin together with cellulose, it has excellent functions of tension, impact, and number of bending bullets. Can be obtained. Further, a resin having a barrier function can be obtained by mixing clay minerals.

  After the mixing and stirring step in step 14, a lamination dehydration step is performed (step 15). In the lamination dehydration step in step 15, the mixed first substance and cellulose are dehydrated by a lamination method. Here, dehydration by the laminating method refers to, for example, a paper basket, a first substance mixed with a net or a frame member stretched with a net and cellulose, and water is removed from the mixture laminated on the net or net and dehydrated. .

  When the second substance having a specific gravity greater than 1 is mixed, the mixing step is performed after the washing and dehydrating step in Step 12, after the ultra-miniaturization step in Step 13, or after the stacking and dehydrating step in Step 15 (Step 16). In the mixing step in Step 16, a second substance having a specific gravity greater than 1 and cellulose are mixed using a kneader or a mixer. Here, the second substance having a specific gravity greater than 1 is a substance that can be used as a new material, for example, carbon, metal, mineral, etc., and when mixing copper fine powder, knead it into a resin together with cellulose. A conductive resin having a conductive function can be obtained. When carbon is mixed, a resin having a function of blocking magnetism and magnetic waves can be obtained by kneading the resin together with cellulose.

A granulation process is performed after the lamination dehydration process in Step 15 or after the mixing process in Step 16 (Step 17).
In the granulation process in step 17, pelletization with a water content of 20 to 30% is performed with a pelletizer.

  After the granulation process in step 17, a drying process is performed (step 18). In the drying process in step 18, drying is performed with vibration or hot air.

As described above, according to the present example, before performing the cooking process in step 8, because kenaf is appropriately refined by two-stage dry grinding, the amount of chemicals in the cooking process can be reduced and the cooking time can be reduced. In addition, since the kenaf has not been refined, it is easy to handle after the cooking process.
Moreover, according to the present Example, generation | occurrence | production of mold | fungi can be prevented by using a bleaching agent. In addition, since the cellulose subjected to the hydrophobization treatment is improved in water dispersion, the fibers are smoothly loosened and pulverized in the ultrafine process, and the ultrafine process is facilitated.

  The method for refining kenaf cellulose according to the present invention is suitable for using annual cellulose such as tomato and sunflower.

Claims (3)

A washing process for washing the introduced kenaf;
A dehydration step of dehydrating the kenaf washed in the washing step;
A drying step of drying the kenaf dehydrated in the dehydration step;
A crushing step of crushing the kenaf dried in the drying step to 6 to 8 mm by crushing by a dry method;
Crushing step of crushing the kenaf crushed by the crushing step to 1 to 3 mm by crushing by a dry method;
A cooking step of cooking the kenaf pulverized in the pulverization step using a chemical liquid mainly composed of caustic soda and sodium sulfide;
A solid-liquid separation step of separating a liquid from the cellulose digested in the cooking step;
The cellulose separated in the solid-liquid separation step, after washing and dewatering, a refinement step for refining with a wet millstone mill,
Bleaching and hydrophobizing step of bleaching and hydrophobizing the cellulose refined in the micronization step using a bleaching agent and a surfactant,
A washing and dehydration step of washing and dehydrating the cellulose bleached and hydrophobized in the bleaching and hydrophobizing step;
A granulation step of pelletizing the cellulose that has been washed and dehydrated in the washing and dehydrating step with a pelletizer;
And a drying step of drying the cellulose pelletized in the granulation step. The cellulose that has been washed and dehydrated in the washing and dehydration step is subjected to an ultrafine refinement step before the granulation step by a wet millstone mill.
After the ultrafine process, a mixing and stirring process in which the first substance having a specific gravity of 1 or less and the cellulose are stirred with a solvent;
After the mixing and stirring step, including a lamination dehydration step of dehydrating the mixed first substance and the cellulose by a lamination method,
2. The method for refining kenaf cellulose according to claim 1, wherein the granulation step is performed after the lamination dehydration step. The cellulose that has been washed and dehydrated in the washing and dehydration step is subjected to an ultrafine refinement step before the granulation step by a wet millstone mill.
After the ultrafine process, having a mixing step of mixing the cellulose and a second substance having a specific gravity greater than 1,
2. The method for refining kenaf cellulose according to claim 1, wherein the granulating step is performed after the mixing step.